楼主你把题目打错啦，不然一个正确答案都没有哦。
这是123题中的72题，

The following SAS program is submitted:

data work.test;
First = 'Ipswich, England';
City = substr(First,1,7);
City_Country=City!!'，'!!'England';
run;

Which one of thefollowing is the value of the variable CITY_COUNTRY in the outputdata set?

A. Ipswich!!
B. Ipswich, England
C. Ipswich, 'England'
D. Ipswich , England

根据书上说的，if the SUBSTR function returns a value to a variable that was not yet assigned a length, by defaulf, the variable length is determined by the length of the first argument.
if you omit the length, SAS extracts the remainder of the expression

所以答案是D，表明了City的长度不止7，后面应该有空格才对。

谢谢 我还没懂 我的d不是也有空格吗