Try not to cough more than you can---since it may cause prob

看一下以下例句你就懂了
Don't lose more than you can help at the casino。你赌博可别把裤子都输掉了。
Don't tell him more than you can help。点到为止。
Don't change it any more than you can help (that is,"any more than you have to" )。除非万不得已,否则就不要再改变什么了（也就是说,“除非你不得不”）。
文中意思,不到万不得已,别咳得太多,因为会造成肺部问题
再问： If we __now to protect the environment,we'll live to regret it。 A。hadn't acted B。haven't acted C。don't act D。won't act 如何区分B,C选项
再答： B。haven't acted 是现在完成时，很明显，保护环境是当下及以后要做的事，而不是已完成的 所以要选c 大意： 如果我们现在不采取行动来保护环境，我们将来就会活在后悔之中