正常小儿20个乳牙出齐的时间为下列哪一年龄阶段
A．20个月
B．28个月
C．2岁半
D．3岁
E．3岁半
参考答案：C
已知点P（3，-1），则点P关于x轴对称的点Q______．
They desired that they __________ the right to attend the meeting.[ ]
A. had
B. have
C. are
D. were
