问题补充：
什么时候difficulty用于复数、什么时候用于单数 英语
答案：
【答案】 1.difficulty n.困难,艰难,难事；有可数名词和不可数名词两种用法
①用作不可数名词,意为困难、艰难,常用在以下句型中
have no/find(some,any,much) difficulty with sth./(in) doing sth.
There is no (some,any,much) difficulty (in) doing sth.
I had no difficulty in learning English.
There was much difficulty (in) explaining it to him.
②用作可数名词,表示具体的困难,意为难事,难点,困境,难处.
This book is full of difficulties.
In face of so many difficulties,we never appeared to be afraid.
