问题补充:
. Tom as well as his classmates a song when the teacher came into the classroom.
A. are singing
B. were singing
C. is singing
D. was singing
答案:
A. are singing
B. were singing
C. is singing
(答案→)D. was singing
解析:考查主谓一致。as well as连接两个主语时,谓语动词取决于前者,句意:当老师进入教室的时候,不仅汤姆的同学而且汤姆当时正在唱歌。根据语境表示过去某一时刻进行的动作应用过去进行时态,所以选D。