已知1999amb3与-11a2bn是同类项，则-mn=______．
由同类项的定义可知m=2，n=3，
所以-mn=-23=-8．
故答案为：-8．
— It is a pity that we have nothing to refer to when we come across new words.
— I quite agree with you. There isn't any dictionary around when we need ______.
A．it
B．that
C．this
D．one
气随伞脱的生理基础是
A．气能生血B．气能摄血C．气能行血D．血能载气E．血能生气
