求高人解答几个SAS BASE123的题目-经管之家官网！

1.
The following SAS program is submitted:
data work.flights;
destination = 'CPH';
select(destination);
when('LHR') city = 'London';
when('CPH') city = 'Copenhgen';
otherwise;
end;
run;这个程序谁能说明下么，其中的SELECT 和WHEN都用什么用处了
2.
The SASDATA.BANKS data set has five observations when the following SAS
program is submitted:
libnamesasdata 'SAS-date-library';
data allobs;
set sasdata.banks;
capital=0;
do year = 2000 to 2020 by 5;
capital + ((capital+2000) * rate);
output;
end;
How many observations will the ALLOBS data set contain?
A. 5
B. 15
C. 20
D. 25
这道题目选的D，我想知道的是RATE这个应该是变量吧，可是没有看到定义语句，这个能这么用么
3.
QUESTION 33
The contents of the raw data file TEAM are listed below:
----|----10---|----20---|----30
Janice 10
Henri 11
Michael 11
Susan 12
The following SAS program is submitted:
data group;
infile 'team';
input name $15. age 2.;
file 'file-specification';
put name $15. =5 age 2.;
run;
Which one of the following describes the output created?
A. a raw data file only
B. a SAS data set named GROUP only
C. a SAS data set named GROUP and a raw data file
D. No output is generated as the program fails to execute due to errors.