问题如下：
For a typical ETF, which of the following sources of tracking error is most likely to be the smallest contributor to tracking error ?
选项：
A. Representative sampling
B. Fees and expenses incurred by the ETF
C. Changes to the underlying index securities
解释：
C is correct. Although additions and deletions of securities from the underlying benchmark index may occur and result in tracking error, such index changes generally occur infrequently (often quarterly). In addition, ETF portfolio managers may work with APs for index rebalance trades to ensure market-on-close pricing to minimize this source of tracking error. Therefore, the resulting tracking error caused by index changes will not likely be as large as the tracking error caused by representative sampling or by fees and expenses incurred by the ETF.
想问一下A和B，哪个是影响ETF return最大的呢？有这个说法吗？
