Which of the Following Record Validation Rules Requires the User

Multiple Choice

Which of the following record validation rules requires the user to enter a value into either Field1 or Field2,but not into both fields?

A) ([Field1] is Null) XOR ([Field2] is Null)
B) [Field1] < > [Field2]
C) (([Field1] > [Field2]) AND [Field2] >10) )
D) none of the above