the teacher expected the students were very excited after hearing the good news.A. AsB.

问题补充：

the teacher expected, the students were very excited after hearing the good news.

A. As

B. So

C. What

D. /

答案：

(答案→)A. As

B. So

C. What

D. /

解析：本题考查定语从句。句意为：正如老师所预料的，听到这个好消息后学生们很兴奋。as引导非限制性定语从句，指代主句整个句子的内容，位置比较灵活，可以位于主句前面，中间或后面，一般用逗号与主句隔开，而 which 所引导的非限制性定语从句只能放在主句之后。