When a set of objects are chosen from a larger set in which the order of the object doesn't matter, we call this combination. Otherwise if the order of selection would matter this would be called a permutation. Probability is the likelihood of selecting a particular specified object in from a specified group of objects. Therefore our answer is B.
Assuming the trapezoids are to scale, they are not the same shape. This means that they could not be congruent even if they were centered on top of each other.
