The most widely accepted theory about the beginning of drama is based on the concept dram

问题补充：

The most widely accepted theory about the beginning of drama is based on the concept drama evolved from ritual.

A. which

B. that

C. when

D. as

答案：

A. which

(答案→)B. that

C. when

D. as

解析： 四个选项分别表示哪一个、那个、什么时候和随着。根据前置词concept内容不可数名词，可知选B,戏剧由宗教仪式发展而成的内容。