Given the two data sets: one and two
One         
# Variable Type  Len Pos
2  sales     Num  8     8
1  year      Num  8     0

Two
# Variable Type  Len Pos
2   budget Num   8     8
3   sales   Char    8     16
1   year    Num    8     0

Date Set ONE has 100 observations, data set Two has 50 observations.
Both dataset have been sorted by Year.
The following SAS program has been submitted:
data three;
   merge One Two;
   by year;
run;
Which one is the result of the program execution?
A.No message written to SAS log
B. Error and warnings are written to SAS log
C. Data set Three is created with three variables and 100 observations
D.Data set Three is created with two variables and 50 observations
请教各位大大，这一题为什么选B不选C？有什么错误吗？