4．将一个正六面体骰子连掷两次，它们的点数都是4的概率是····························· （▲）
A． B． C． D．
5．化简 的结果为················································································· （▲）
A． 1 B．1 C． D．
6．要使分式 有意义，则 的取值范 围是························································ （▲）
A． ≠1 B． ＞1 C． ＜1 D． ≠ 1
7．如图， 是四边形ABCD的对称轴，AD∥ BC，下列结论：①AB∥CD；②AB＝BC；③AB⊥BC；④AO＝CO，其中正确的有·············································································································· （▲）
