Java语言通过接口支持_______继承，使类继承具有更灵活的扩展性。
参考答案：多重
It was hard for him to learn English in a family, in which _____ of the parents spoke the language.
A．none
B．neither
C．both
D．Each
下列函数中偶函数的个数是（）。
A．0
B．1
C．2
D．3
