假定A为自变量,B为因变量,弹性的数学表达式为( )

A、<span lang="EN-US" style="font-size:14.0pt;font-family: &quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning:1.0pt; mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA">E=</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;; mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family:&quot;Times New Roman&quot;; mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN; mso-bidi-language:AR-SA">（Δ</span><span lang="EN-US" style="font-size:14.0pt; font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning: 1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language: AR-SA">B/</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family: &quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family: &quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language: ZH-CN;mso-bidi-language:AR-SA">Δ</span><span lang="EN-US" style="font-size:14.0pt; font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning: 1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language: AR-SA">A</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family: &quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family: &quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language: ZH-CN;mso-bidi-language:AR-SA">）·（</span><span lang="EN-US" style="font-size: 14.0pt;font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体; mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN; mso-bidi-language:AR-SA">A/B</span><span style="font-size:14.0pt;font-family: 宋体;mso-ascii-font-family:&quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;; mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language: EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA">）</span>

B、<span lang="EN-US" style="font-size:14.0pt;font-family: &quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning:1.0pt; mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA">E=</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;; mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family:&quot;Times New Roman&quot;; mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN; mso-bidi-language:AR-SA">（Δ</span><span lang="EN-US" style="font-size:14.0pt; font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning: 1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language: AR-SA">A/</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family: &quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family: &quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language: ZH-CN;mso-bidi-language:AR-SA">Δ</span><span lang="EN-US" style="font-size:14.0pt; font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning: 1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language: AR-SA">B</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family: &quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family: &quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language: ZH-CN;mso-bidi-language:AR-SA">）·（</span><span lang="EN-US" style="font-size: 14.0pt;font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体; mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN; mso-bidi-language:AR-SA">B / A</span><span style="font-size:14.0pt;font-family: 宋体;mso-ascii-font-family:&quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;; mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language: EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA">）</span>

C、<span lang="EN-US" style="font-size:14.0pt;font-family: &quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning:1.0pt; mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA">E=</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;; mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family:&quot;Times New Roman&quot;; mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN; mso-bidi-language:AR-SA">（Δ</span><span lang="EN-US" style="font-size:14.0pt; font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning: 1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language: AR-SA">B/ B</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family: &quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family: &quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language: ZH-CN;mso-bidi-language:AR-SA">）·（Δ</span><span lang="EN-US" style="font-size: 14.0pt;font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体; mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN; mso-bidi-language:AR-SA">A/A</span><span style="font-size:14.0pt;font-family: 宋体;mso-ascii-font-family:&quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;; mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language: EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA">）</span>

D、<span lang="EN-US" style="font-size:14.0pt;font-family: &quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning:1.0pt; mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA">E=</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;; mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family:&quot;Times New Roman&quot;; mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN; mso-bidi-language:AR-SA">（</span><span lang="EN-US" style="font-size:14.0pt; font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning: 1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language: AR-SA"> B /</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family: &quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family: &quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language: ZH-CN;mso-bidi-language:AR-SA">Δ</span><span lang="EN-US" style="font-size:14.0pt; font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体;mso-font-kerning: 1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN;mso-bidi-language: AR-SA">B</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family: &quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family: &quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language: ZH-CN;mso-bidi-language:AR-SA">）·（</span><span lang="EN-US" style="font-size: 14.0pt;font-family:&quot;Times New Roman&quot;,&quot;serif&quot;;mso-fareast-font-family:宋体; mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN; mso-bidi-language:AR-SA">A/</span><span style="font-size:14.0pt;font-family: 宋体;mso-ascii-font-family:&quot;Times New Roman&quot;;mso-hansi-font-family:&quot;Times New Roman&quot;; mso-bidi-font-family:&quot;Times New Roman&quot;;mso-font-kerning:1.0pt;mso-ansi-language: EN-US;mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA">Δ</span><span lang="EN-US" style="font-size:14.0pt;font-family:&quot;Times New Roman&quot;,&quot;serif&quot;; mso-fareast-font-family:宋体;mso-font-kerning:1.0pt;mso-ansi-language:EN-US; mso-fareast-language:ZH-CN;mso-bidi-language:AR-SA">A</span><span style="font-size:14.0pt;font-family:宋体;mso-ascii-font-family:&quot;Times New Roman&quot;; mso-hansi-font-family:&quot;Times New Roman&quot;;mso-bidi-font-family:&quot;Times New Roman&quot;; mso-font-kerning:1.0pt;mso-ansi-language:EN-US;mso-fareast-language:ZH-CN; mso-bidi-language:AR-SA">）</span>