During the installation of the groove, the total cross-sectional area of the conductor including insulation in the same groove shall not exceed the inner cross-sectional area of the groove. （ ） 。
在线槽安装过程中，同一线槽内包括绝缘在内的导线截面积总和应该不超过线槽内部截面积的 （ ） 。

A. 20%

B. 40%

C. 60%

D. 80%