在备考adv中发现63题的答案有出入，想请大神帮忙看一下。
第一题，When attempting to minimize memory usage, the most efficient way to do group processing when using the MEANS procedure is to use:
A. The BY statement
C. The CLASS statement
米粮包里的答案是C，Crackman写的是A。

我查了一下sas support是这样写的：
Using the BY statement with PROC MEANS：
When you use the CLASS statement and class variables in PROC MEANS, the memory requirements can be substantial. SAS keeps a copy of unique values of each class variable in memory. If PROC MEANS encounters insufficient memory for the summarization of all class variables, you can save memory by using the CLASS and BY statement together to analyze the data by classes.
看起来像A？

然后有朋友说因为by statement要sort 所以是C？

第57题，which of the following is true about the COMPRESS=YES data set option?
B. It is most effective with character data that contains repeated characters.
D. It is most effective with character data that contains patterns, rather than simple repetitions.
米粮包里的答案是D，Crackman写的是B。

我查了一下sas support，Data set compression using COMPRESS=。里面有一句the option COMPRESS=YES is effective with character data that contains repeated characters such as blanks. 所以选B？


谢谢啦！