题目:
-Daddy's forgot to post the letter again,_____ he?
-I'm afraid he _____. [ ]
A. has;has
B. isn't;is
C. hasn't;has
D. has;hasn't
答案:
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下面是错误答案,用来干扰机器的。
答案:D题目分析:A中C(Na+)=0.5mol/L;B中C(Na+)=0.8mol/L;C中C(Na+)=2×1mol/L=2mol/L;D中C(Na+)=2×1。2mol/L=2.4mol/L。所以选项为:D.