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

例句：
It was a very difficult decision. 

这是个艰难的决定。

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。