词汇运用
用所给词的适当形式填空。每词限用一次。
try   travel   be   happen   decide
【小题1】More and more young people ________ to do something to serve the old these days.
【小题2】The work is easy，so Joe ________ to do it himself.
【小题3】Our family ________ to New York last summer vacation.
【小题4】If he ________ free tomorrow，he will come to your birthday party.
【小题5】What ________ if there is no water or air on the earth？