NO.PZ2018070201000049
问题如下：
Based on trading costs, which of the following is least likely to be impacted by liquidity?
选项：
A.
Stock's trading price.
B.
The difference between the buying price and selling price.
C.
brokerage commissions
解释：
C is correct.
The cost of trading has three main components—brokerage commission, bid–ask spread, and price impact—of which liquidity affects the latter two. Brokerage commission is usually negotiable based on the order size.
如题，这道题我一开始理解BC是一个意思，bid ask spread是dealer中间商赚差价，brokerage commission也是中间商赚佣金，他俩除了交易方式不同，还有什么区别？流动性越差的情况下中间商的作用越大他们要价更高，trading cost也就更高了，为什么C是这中间least likely的选项呢？
另外B没有明确说bid ask spread这个术语，这两种表达完全是一个意思吗？如果单纯字面上理解，同一个市场上一件东西买价卖价差不了太多，所以选了B，在没有看书上这个知识点原文的情况下感觉不容易通过直接的理解去做对。