问题如下：
One month after inception, the price return version and total return version of a single index (consisting of identical securities and weights) will be equal if:
选项：
A.market prices have not changed.
B.capital gains are offset by capital losses.
C.the securities do not pay dividends or interest.
解释：
C is correct.
The difference between a price return index and a total return index consisting of identical securities and weights is the income generated over time by the underlying securities. If the securities in the index do not generate income, both indices will be identical in value.
考点：total return和 price return的区别
这道题问我们的是在什么情况下，用total return和 price return计算指数收益率是相等的。我们计算指数total return要考虑期间的现金流（股息）,而price return不包括期间收益。它俩的差别在于期间收益，因此这道题只能选C。当股票不发红利时两种计算指数收益率的方法得到的结果相等。
可以再具体讲一下 interest的意思么？
