Which two tasks would require sub queries or joins in order to be performed in a single step?

The COMMISSION column shows the monthly commission earned by the employee.

Which two tasks would require sub queries or joins in order to be performed in a single step?
(Choose two.)

A.
listing the employees who earn the same amount of commission as employee 3

B.
finding the total commission earned by the employees in department 10

C.
finding the number of employees who earn a commission that is higher than the average
commission of the company

D.
listing the departments whose average commission is more that 600

E.
listing the employees who do not earn commission and who are working for department 20 in
descending order of the employee ID

F.
listing the employees whose annual commission is more than 6000