令a=1，那么：
a÷
a÷7×3=1÷7×3=
故答案为：错误．
(2013·陕西咸阳一模)—Hi, Tom. Do you still smoke?
—________. It's three years since I smoked.
A．No, I don't
B．Yes, I do
C．Not too much
D．Oh, yes, but I wish I didn't
由权值为5，9，2，6的4个叶子构造一棵哈夫曼树，该树的带权路径长度为 。
A．21 B．22 C．42 D．44
