what if
what will happen if；what is the difference if；suppose that假设…；如果…，该怎么办
I don't like to have you go boating in such weather．What if a storm should come up？我不想让你在这样的天气里去划船，要是刮起了大风暴怎么办？
What if he doesn't come？We can not do without him．如果他不来怎么办？没有他，我们就无法干。