though B【解析】试题分析：根据句意根据厂里的规章制度，如果你有医生的诊断书，你才能请假。故选B

While I_______ a detective story, someone_______ at the door．

What are theydoing-They are talking the phonetheir life.

It takes 3 hours_________ from jiangyin to Shanghai _______ a bus.

This kind of exercise is most _____, and therefore is a good test of you students’ ability. [ ]