More than 20 people in traffic accidents last May.A. died; forB. have been dead; sinceC.

问题补充：

More than 20 people in traffic accidents last May.

A. died; for

B. have been dead; since

C. have died; for

D. have been dead, for

答案：

A. died; for

(答案→)B. have been dead; since

C. have died; for

D. have been dead, for

解析：since在引导时间状语时，后面接时间点；for在引导时间状语时，后面接一段时间。根据下文last May即可断定选B。句意：自从去年五月以来，超过20人死于交通事故。结合语境可知本句描述的是现在已经完成的动作，用现在完成时态。