difficult 
英 [ˈdɪfɪkəlt]  美 [ˈdɪfɪˌkʌlt] 
adj. 困难的；执拗的；不易相处的

例句：
The first question was the most difficult. 

第一个问题最难。

This decision is difficult to understand. 

这个决定让人难以理解。

It's difficult to choose. 

很难作出选择。

I find it difficult to speak up for myself. 

我觉得为自己辩护很难。

It's difficult for single mothers to get jobs. 

单身母亲很难找到工作。

We do owe them, so it's difficult for us to say no. 

我们确实欠他们的人情，所以很难对他们说不。