问题如下：
Which of the following risk premiums is most relevant in explaining the difference in yields between 30-year bonds issued by the US Treasury and 30-year bonds issued by a small private issuer?
选项：
A.Inflation
B.Maturity
C.Liquidity
解释：
C is correct.
US Treasury bonds are highly liquid, whereas the bonds of small issuers trade infrequently and the interest rate includes a liquidity premium. This liquidity premium reflects the relatively high costs (including the impact on price) of selling a position.
What does "selling position" mean, mention in the explanation part. Thanks
