From the list below, select every sentence that must be true.
A. If and the sets are mutually disjoint, then .
B. If is a finite sample space and is an event in , then .
C. Assume we are making passwords using lower-case letters. The number of passwords of length 3 or 4 is equal to the number of passwords of length 3 plus the number of passwords of length 4.
D. The number of two digit integers divisible by or is equal to the number of two digit integers divisible by plus the number of two integers divisible by .