Mr.Smith as well as his students, ________ a song in English when I came in．

A.sang

B.were singing

C.was singing

D.is singing

答案及解析： C

解析：

此题考查主谓一致。句子的主语是Mr．Smith, as well as连接的成分不作主语，因此谓语动词要用单数，受“when I came in”从句限制，要用过去进行时。