Answer: 1/216 (choice B)
Reason:
There are 6 sides to the number cube. It gives 6*6*6 = 216 ways to roll three such dice. Only one of those ways has the sequence "1,1,1" that we're after. Therefore, the probability is 1/216.
It roughly approximates to 0.0046296; which is about a 0.46% chance of happening.
This all assumes that each side is equally likely. The answer will be different if the die is loaded in some fashion.