“It” is often used to a baby.
A．mean to
B．stick to
C．point to
D．refer to
答案：D
国家建立全国统一的个人社会保障号码。个人社会保障号码为（）。
A.社保经办机构派发的号码
B.公民身份号码
C.社保征收机构派发的号码
D.随机滚动生成的号码
Every solid object ______ reflect a sound，varying according to the size and nature of the object．
A．must
B．shall
C．will
D．should
