csc chapter 18

老师您好，
关于18章问题survivorship bias tends to 
a. inflation returns and overstate assets under management 
b. inflation returns and under assets under management 
为何选b而不是a？
书上说 “This term describes a tendency for poorly performing funds to be discontinued or merged. Therefore, average returns of surviving funds may be artificially high because they do not fully reflect past performance of the entire spectrum of funds.”
以我的理解应该是因为幸存下来的股票应该有相应较高的回报率 没有真实反映出市场上真正return， 所以为何不是overstate assets呢？