1. I was unable to recollect the names.
    我回想不起那些名字了。

2. I knew my sadness came not only from missing my family, but also from the frustration of being unable to learn.
    我知道我的难受不仅仅是因为想念家，而且是因为自己无法集中精力学习而感到的沮丧。

3. In contrast, the kids who grabbed the one piece of candy were, as teenagers, more likely to be inflexible, unable to make decisions and stressed.
    相反，那些当初迫不及待地吃了第一块糖的孩子到了十几岁时更有可能表现得缺乏灵活性，难以作决定，容易紧张。