Apizza shop offers 12 different topping choices. if you order a large pizza with two toppings, how many possibilities would you have?

This is the concept of combinations, the solution to our question will be:
The number of combinations of 12 things take 2 at a time is
12C2
=(12!)/[(12-2)!2!]
=(12!)/(10!*2!)
=12*11/2
=66

66

B, 0.4 repeats so it is rational and square root of 16 is 4 so that is rational as well.