1. worry about 担心
例句:Don't worry about him; he is a cheerful and elastic man.
别为他担心;他是个快活开朗的人WPuzNTk2;Q。

2. be associated with 与......有关
例句: A heavy infection with F. hepatica may be associated with roughened hair coats.
肝片吸虫的重度感染，可伴有被毛粗乱F1HRMc|VUCj-mnMS|R。

3. hard to know 很难知道
例句: It's hard to know how to say this tactfully.
不知道怎样才能婉转地讲明这件事7[VALTuC^OQ7L0Rkjj%。

4. try to do sth 努力去做某事

例句: Also, try to avoid abbreviations. If you must abbreviate, use standard abbreviations.
避免用缩略语，如果必须，要用标准缩略语xpD8,AipE+5*9o=。

5. how often 多久一次

例句：How often do you go swimming?

你多久去游一次泳？