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
