all over again 再一次,重新

a big headache令人头痛的事情

a fraction of 一部分

a matter of concern 焦点

a series of 一系列,一连串

above all 首先,尤其是

absent from不在,缺席

abundant in富于

account for 解释

accuse sb. of sth.控告

agree with同意

ahead of time / schedule提前

ahead of 在...之前（ahead of time 提前）

alien to与...相反

all at once 突然,同时

all but 基本上;除了...都

all in all 总之

all of a sudden 突然

certainly 当然地；无疑地

obviously 显然