Item 48
Given the following program and data:
data WORK.BDAYINFO;
infile datalines;
input Name $ Birthday : mmddyy10.;
datalines;
Alan 11/15/1950
Barb 08/23/1966
Carl 09/01/1963
;
run;
%let Want=23AUG1966;
proc print data=WORK.BDAYINFO;
[_insert_statement_]
run;
What is the WHERE statement that successfully completes the PROC PRINT and selects the observation for Barb?
A. where Birthday=&Want;
B. where Birthday=“&Want”;
C. where Birthday=“&Want”d;
D. where Birthday=‘&Want’d;
答案是C  ，但是为什么D不行呢？我试过了，where Birthday = ‘23AUG1966’d和where Birthday = “23AUG1966”d都可以，为什么换成宏变量就不行了呢？求大神解答