问题如下图：
选项：
A. 
B. 
C. 
解释：
a选项什么意思呢？怎么理解？答案解释也不是很明白
NO.PZ2017121002000004 问题如下 Corporate bonseconry market trang most often occurs: A.on a book-entry basis. B.on organizeexchanges. C.prior to settlement T + 1. A is correct.The vast majority of corporate bon are train over-the-counter (OTmarkets thuse electronic trang platforms through whiusers submit buy ansell orrs. Settlement of tras in the OTC markets occurs means of a simultaneous exchange of bon for cash on the books of the clearing system \"on a paperless, computerizebook-entry basis.\"考点corporate bon析Book-entry basis理解成电子记账系统；债券所有者没有Physical凭证，债券的所有权关系计入电子系统，故A正确。 Prior to settlement T+1的意思不是指 T+1是在结算之前吗？
NO.PZ2017121002000004问题如下Corporate bonseconry market trang most often occurs:A.on a book-entry basis.B.on organizeexchanges.C.prior to settlement T + 1. A is correct.The vast majority of corporate bon are train over-the-counter (OTmarkets thuse electronic trang platforms through whiusers submit buy ansell orrs. Settlement of tras in the OTC markets occurs means of a simultaneous exchange of bon for cash on the books of the clearing system \"on a paperless, computerizebook-entry basis.\"考点corporate bon析Book-entry basis理解成电子记账系统；债券所有者没有Physical凭证，债券的所有权关系计入电子系统，故A正确。 这个没看到老师讲啊 还是原版书习题 慌了
on organizeexchanges. prior to settlement T + 1. A is correct. The vast majority of corporate bon are train over-the-counter (OTmarkets thuse electronic trang platforms through whiusers submit buy ansell orrs. Settlement of tras in the OTC markets occurs means of a simultaneous exchange of bon for cash on the books of the clearing system \"on a paperless, computerizebook-entry basis.\" 请问强化班14页不是写着T+0价格吗？哪些交割时间是需要掌握的，时间是多少？能帮忙总结一下吗？
b为什么不对？不是统一组织交易么
请问A是什么意思呀？
