钢筋混凝土过梁在洞口两侧伸入墙内的长度，应不小于（  ）。

A、<span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: " times="" new="" roman";="" mso-bidi-font-size:="" 10.0pt;="" 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"="">120mm</span>

B、<span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: " times="" new="" roman";="" mso-bidi-font-size:="" 10.0pt;="" 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"="">180mm</span>

C、<span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: " times="" new="" roman";="" mso-bidi-font-size:="" 10.0pt;="" 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"="">200 mm</span>

D、<span lang="EN-US" style="FONT-SIZE: 10.5pt; FONT-FAMILY: " times="" new="" roman";="" mso-bidi-font-size:="" 10.0pt;="" 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"="">240mm</span>