这个did表强调
请看下面的题：
An awful accident _________, however, occur the other day.
A. does B. did C. has to D. had to
【分析】此题正确答案应选B，句末的 the other day 意为“前几天”，所以句子应用过去时态，而选项D填进去不合题意，故选B。此句有两个难点：一是句中插有 however 一词，分散了同学们的注意力；二是所填选项B为许多同学所不熟悉的强调用法。又如(答案均选B)：
(1) Your mother _________, however, say that to us that day.
A. does B. did C. is doing D. was doing
(2) Our math teacher _________, however, speak English well.
A. doing B. does C. is doing D. was doing