1. a big headache令人头痛的事情2. a fraction of 一部分3. a matter of concern 焦点4. a series of 一系列,一连串above all 首先,尤其是5. absent from不在,缺席6. abundant in富于7. account for 解释8. accuse sb. of sth.控告9. add to增加（add up to）10. after all 毕竟,究竟11. agree with同意12. ahead of time / schedule提前13. ahead of 在.之前（ahead of time 提前）14. alien to与.相反15. all at once 突然,同时16. all but 几乎;除了.都17. all of a sudden 突然18. all over again 再一次,重新19. all over 遍及20. all right 令人满意的;可以21. all th
