Mike had just finished his lunch and was about to take a break an unexpected visitor came

问题补充：

Mike had just finished his lunch and was about to take a break an unexpected visitor came.

A. when

B. while

C. so

D. for

答案：

(答案→)A. when

B. while

C. so

D. for

解析：考查连词。be about to … when …正要做……突然……句意：Mike刚吃完午饭正要休息的时候，突然一名不速之客来临，选A。