In which two situations should you use sub-queries? There are 2 correct answers to this question.

In which two situations should you use sub-queries? There are 2 correct answers to this question.
A . When the query filter involves values that are known
B . When the query filter involves values that are not known
C . When the query filter for the report involves a value that will change over time
D . When the query filter for the report involves a value that will never change over time

Answer: B,C