The police said they would not give up looking into other possibilities ____they find out what happened

schedule is made, by strictly _______ it, you can avoid putting off till tomorrow what should be done.

No one knows when such a custom first _____.

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

Shelookssosad.She_____ill.