1.remain to 保持

Some evident problems remain to be sorted out.
仍有些突出问题亟待解决。

And the most important questions remain to be answered.
而最重要的问题仍然没有答案。

2.able to 能；会

He was even able to build his own home.
他现在甚至能建一所自己的房子。

How fortunate that he had been able to love!
能爱别人是多么幸运的一件事！

3.a couple of 两个，几个

We met in moscow a couple of weeks ago.
几周后我们在莫斯科又见了一面。

Within a couple of days, both sons-in-law were killed.
几天内，两位女婿都被杀。