When I try to understand ________ that prevents so many children from being happ

题干

When I try to understand ________ that prevents so many children from being happy, there seem to be three causes.

A．why it is	B．what it does
C．why it does	D．what it is

上一题下一题 0.64难度单项选择更新时间:2016-08-05 05:54:16

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