在准备SAS ADV 考试，手头两套63题中有几道题答案不一致，请朋友指点：
1. 第一题：When attempting to minimizememory usage, the most efficient way to do groupprocessing when using the MEANS procedure is to use:  

  A. the BY statement.     

  B.GROUPBY with the NOTSORTED specification.

  C. theCLASS statement.   

  D.multiple WHERE statements.

请问是A 还是C呢？

2.第7题：

7. A quick rule of thumb forthe space required to run PROC SORT is:

A.two times the size of the SAS data set being sorted.      

B.three times the size of the SAS data set being sorted.   

C. four times the size of the SASdata set being sorted.     

D. five times the size of the SAS data set beingsorted

[size=14.6667px]想确认下答案是C吗？谢谢！

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3. 第57题：

57. Which of the following istrue about the COMPRESS=YES data set option?      

A.It uses the Ross Data Compression method to compress numeric data.  

B. It is most effective withcharacter data that contains repeated characters.

C.It is most effective with numeric data that represents large numericvalues.   

D.It is most effective with character data that contains patterns, rather thansimple repetitions.  

请问是B还是D呢？

多谢各位！