问题如下图：
选项：
A. 
B. 
C. 
解释：
请问B为什么对的？能简单解释一样吗？
NO.PZ2018062006000010 b免税不只是联邦tax吗？不够严禁吧
Municipbon are usually tax-exempt. The originissue scount tprovision requires the investors to pton capitgain maturity. C is correct. The originissue scount tprovision requires the investor to inclu a prorateportion of the originissue scount in his taxable income every tyeuntil maturity. Thus, the cost basis in the bonis increaseeayear, anwhen the bonmatures, there is no capitgain or loss. For exampe, a 10-yezero coupon bonis issue600, anthe pvalue is 1000. The originissue scount is: 1000 - 600 = 400; With originissue scount tprovision, the bons matruity is 10 years, the prorateportion incluin the investors' taxable income eayeis: 400/10 = 40. The cost basis for the first yeis 600, after the first tyear, the cost basis is increaseto 640. The originissue scount tprovision allows investor to increase his cost basis in the bongraally so thwhen the bonmatures, he faces no capitgain or loss.针对答案A，interest income为什么会跟ornary income一样呢，我记得老师提过投资收益和普通的收益税收比例有差异
能解答一下C吗，谢谢
可不可以用中文翻译一下答案的
