从句可以与非谓语动词互换.If you check your composition carefully,you can at least avoid some spelling mistakes.=Checking your composition carefully,you can at least avoid some spelling mistakes.=Check...如果改为when you check,对不对呢可以的，只是由if引导的条件状语从句变为了when引导的时间状语从句，2种情况都可以变成非谓语动词的句子形式。If you check your composition carefully, you can at least avoid some spelling mistakes.=Checking your composition carefully, you can at least avoid some spelling mistakes.如果你仔细检查你的作文，你至少可以避免一些拼写错误。When you check your composition carefully, you can at least avoid some spelling mistakes.=Checking your composition carefully, you can at least avoid some spelling mistakes.当你仔细检查你的作文，你至少可以避免一些拼写错误。