据统计，争取一个新客户的成本是留住一个老客户的（）倍。
A. 3
B. 5
C. 10
D. 16
这篇文章的目的是什么？
A. 介绍会议内容
B. 研究雨林消失的原因
C. 号召人类保护热带雨林
D. 《国际热带木材协定》的内容
The main thing that all bonds have in common is that they______.
A. denote borrowing by whomever issued them
B. have less than twenty years maturity
C. include a coupon payment
D. are issued by corporations
A．spellB．telephoneC．sheD．very
A. spell
B. telephone
C. she
D. very
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