________ she couldn’t understand was ________ fewer and fewer students showed interest in her lessons

May I go out to play with my friends now, Dad—No. You ______ let your mother know first.

Some scientists have sent a spacecraft to Mars. It ____ several months to get there.

He said he would come to attend the lecture if he ___________ time.

下面各句中加点词语的解释有误的一项（ ）