3的绝对值是______．
根据正数的绝对值是它本身，得|3|=3．
The urge to go abroad for further study is strong, but it was not until last summer ________ I knew how powerful it could be.
A．who
B．that
C．where
D．before
《公约》规定禁止由哪些人销售烟草制品？
