It’s clever _____ you to help me work out this difficultmaths problem. Thanks.— You are welcome. Now it’s easier ______ you tounderstand it.

The gate will close ________ two minutes before the train leaves[ ]

19I made a bad impression ________ the teacher ________ arriving late on my first day

. We all think that _____ no need to make laws to prevent the young from getting married during their college life.

下列各句中，加线的成语使用恰当的一项是  （    ）