请问什么是stale pricing，没太明白 问题如下图：
选项：
A. 
B. 
C. 
解释：
NO.PZ201909280100000806 问题如下 6 Whiof Park’s statements regarng the asset allocation approaches is correct? A.Only Statement 3 B.Only Statement 4 C.Both Statement 3 anStatement 4 C is correct. Statement 3 is correbecause risk factor-baseapproaches to asset allocation capplieto velop more robust asset allocations. Statement 4 is correbecause a mean–varianoptimization typically overallocates to the private alternative asset classes, partly because of unrestimaterisk e to stale pricing anthe assumption threturns are normally stributerisk factor approach在配置资产组合时整体会更灵活。还是举个栗子，比如我想模拟一个创业板指数的走势，但是这些指数里面有些个股可能很难买到（比如因为交易不活跃）。那这个时候用risk factor approach来代替，做一个类似这些很难买到的指数里的个股的risk factor 。（例如这个买不到指数里的个股是小股票c，受小市值因子影响很大，就做多一个小市值股票同时做空一个大市值的股票，模拟出c股票的类似走势，即使没有买c股票，但是想要的结果达到了，用的risk factor approach模拟的结果涨跌和c股票都差不多）这样就相对更灵活一些，不用买不到这个指数的个股干着急。因为价格更新的慢，样本少了，平滑了波动，所以方差小，而真实的波动会大很多，所以会低估风险，进而分配过多的资产在private alternative asset。所以选 robust这个词不管是在英语词典或是“电气自动化”专业论文里都是“稳健，稳定的”意思，为什么这里理解的是灵活呢？
NO.PZ201909280100000806 A中的robust是什么意思？能把A一下吗
NO.PZ201909280100000806 3 说的是啥啊。。。
NO.PZ201909280100000806 statement 4中的前半句是正确的，后面的stale pricing为什么是正确的？
NO.PZ201909280100000806 Only Statement 4 Both Statement 3 anStatement 4 C is correct. Statement 3 is correbecause risk factor-baseapproaches to asset allocation capplieto velop more robust asset allocations. Statement 4 is correbecause a mean–varianoptimization typically overallocates to the private alternative asset classes, partly because of unrestimaterisk e to stale pricing anthe assumption threturns are normally stribute 风险因子方法不是有implementation hures吗？
