问题如下：
Considering kinds of principal repayment structures, which one of them is the most similar to the sinking fund arrangement for bond issuers?
选项：
A.Coupon payment structure.
B.Serial maturity structure.
C.Term maturity structure.
解释：
B is correct.
The serial maturity structure is that the company issues a series of bonds and the bond holders know which bonds will mature. But the bonds retired annually with a sinking fund arrangement are designed by a random drawing. The bondholders don’t know which part of bonds be paid off each year. But both of them result in portion of the bond issue being paid off each year. So the serial maturity structure is the most similar one to the sinking fund arrangement.
这个题请帮忙解释下，谢谢。
