计算：（x3-2x2y）÷（-x2）
（x3-2x2y）÷（-x2），
=x3÷（-x2）-（2x2y）÷（-x2），
=-x+2y．
There are many reasons why some children have bad manners, ______ is the ill information on the Internet and in TV programme．
A．one of them
B．it
C．one of which
D．that
己内酰胺装置硫铵萃取塔中（）为分散相。
A、苯
B、硫铵
C、粗油
D、水
