Mr. Fox fell ill, thus __________ itnecessary for us to find another person for his job.

Modern science has given clear evidence ________ smoking can lead to many diseases.(2011·天津，13)

I am going to have a job interviewtomorrow morning.—Well, ________________

.To improve your health, you can _________ 25— 30 minutes three or four times a week to do simple things such as walking ,cycling or running .

下列各句中，加点的成语使用恰当的一项是（）。