[译] 他不费力就找到了我家。
[误] He had no difficulties in finding my house.

[正] He had no difficulty in finding my house.
[注] “have no/some difficulty in doing something”是一个句型，意思是“做某事没有/有些困难”，在这个句型中，difficulty 是一个不可数名词，没有复数形式的变化。但 difficulty 表示具体困难时，又是一个可数名词了。比较：We have overcome one difficulty after another. 我们克服了一个又一个困难。