answer the call of nature可不是回应大自然的呼唤，而是解手；上厕所。

【例句】
Does anyone need to answer the call of nature before we set off?
我们准备出发了，有谁想上冼手间？

Sorry, sir, I must answer the call of nature& I won't be long.
对不起先生，我得去方便一下，就一会儿。