问题如下：
Notching means a difference in credit rating between :
选项：
A.an issue and an issuer.
B.an investment grade and a non-investment grade.
C.a company and its industry.
解释：
A is correct.
A borrower may have multiple debt issues that vary by credit rating.
Notching refers to the practice of adjusting an issue credit rating upward or downward from the issuer credit rating to reflect the seniority and the other provisions of a debt issue.
为什么不选B？不是一个人发行人发行不同的债券吗
