What is the difference between a SetUID and SetGID bit?

What is the difference between a SetUID and SetGID bit?
A . SetUID applies to files, while SetGID applies to directories
B . SetUID allows a file to be executed with the permissions of the file owner, while SetGID allows a file to be executed with the permissions of the group owner
C . SetUID allows a user to change the owner of a file, while SetGID allows a user to change the group owner of a file
D . There is no difference between SetUID and SetGID

Answer: B