312不是最简分数，化简后是14，分母中只含有质因数2，能化成有限小数．
故判断为：错误．
课文填空。按照课文填出下列各句中缺少的词汇，每空一词。
A. In fifteen terrible seconds a large city lay in 1_____.
B. Although she didn't know the best way of getting to places, she insisted that she 2_____ the trip properly.
C. Geography also 3_____ a part in 4_____ dialects.
D. I can well remember that there was a time when a deep blue sky, the song of the birds, moonlights and
flowers 5_____ never 6_____ 7_____ me spellbound.
E. He was 8_____ with his time, for which I was grateful.
F. He was the first man 9_____ land on the moon in July 1969.
G. A great person is someone who 10_____ his life to helping others.
在PKI的性能要求中，电子商务通信的关键是（ ）
A．支持多政策
B．支持多应用
C．互操作性
D．透明性
