为避免学生过于斜视而影响视力，水平视角及前排边座与黑板远端的视线夹角应大于等于（ ）度

A、<span lang="EN-US" style="FONT-SIZE: 10pt; FONT-FAMILY: " times="" new="" roman";="" mso-font-kerning:="" 1.0pt;="" mso-ansi-language:="" en-us;="" mso-fareast-language:="" zh-cn;="" mso-bidi-language:="" ar-sa;="" mso-fareast-font-family:="" 宋体"="">10</span>

B、<span lang="EN-US" style="FONT-SIZE: 10pt; FONT-FAMILY: " times="" new="" roman";="" mso-font-kerning:="" 1.0pt;="" mso-ansi-language:="" en-us;="" mso-fareast-language:="" zh-cn;="" mso-bidi-language:="" ar-sa;="" mso-fareast-font-family:="" 宋体"="">15</span>

C、<p><span lang="EN-US" style="FONT-SIZE: 10pt; FONT-FAMILY: " times="" new="" roman";="" mso-font-kerning:="" 1.0pt;="" mso-ansi-language:="" en-us;="" mso-fareast-language:="" zh-cn;="" mso-bidi-language:="" ar-sa;="" mso-fareast-font-family:="" 宋体"="">20</span></p>

D、<p><span lang="EN-US" style="FONT-SIZE: 10pt; FONT-FAMILY: " times="" new="" roman";="" mso-font-kerning:="" 1.0pt;="" mso-ansi-language:="" en-us;="" mso-fareast-language:="" zh-cn;="" mso-bidi-language:="" ar-sa;="" mso-fareast-font-family:="" 宋体"="">30</span></p>