本人SAS 新手一枚，请大神帮忙解释下下面的程序：

The following SAS program is submitted:
data WORK.NEW;
do i=1, 2, 3;
Next=cats(‘March’ || i );
infile XYZ
filevar=Next
end=Eof;
do until (Eof);
input Dept $ Sales;
end;
end;
run;
The purpose of the FILEVAR=option on the
INFILE statement is to name the variable
Next, whose value:

A.points to a new inputfile.

B.is output to the SAS data set WORK.NEW.

C.is an input SAS data set reference.

D.points to an aggregate storage location.


[size=13.3333330154419px]这里我有几个问题，1. cats函数括号里面的 ll是什么意思？2. end=(eof)这个不太明白 3. 题目的问题。
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[size=13.3333330154419px]谢谢大家！！！