1、lack，缺乏，词组:be lack of 缺乏。We are lack of  water very much.我们十分缺乏水资源。

2、back，背部，The back pain left the patient suffering.

背部疼痛让这个病人受尽了折磨。例：

He opened the back door.

他打开了后门。

Ann could remember sitting in the back seat of their car.

安能记得曾坐在他们车子的后座上。