Which of the following collections is not a set?

If A, B, C are any three sets, then A × (B U C) is equal to:

If A = {1, 2} and B = {3, 4}, then the number of relations from A to B is:

Let R be a relation on the set N of natural numbers defined by nRm if n divides m. Then R is:

The domain of the function f(x) = √(9 - x²) is:

The range of the function f(x) = |x| is:

If f(x) = x² and g(x) = 2x + 1, then (f + g)(2) is:

Let R be a relation from a set A to a set B. Then:

The function f: R → R defined by f(x) = x² is:

The domain of the function f(x) = 1 / (x - 2) is:

If A has 3 elements and B has 4 elements, then the number of elements in A × B is:

The range of the constant function f(x) = c is: