Hello,
The answer is option B "84".
Reason:
LCM (Least, Common, Multiple) therefore it means that the least number that two numbers are divisible bye therefore the answer is 84 because its the least number the the two numbers are dividable by. Therefore the newer is option B. Just remember Least, Common, Multiple.
If you need anymore help feel free to ask me!
Hope this helps!
~Nonportrit