If cardinality of (AUB) = cardinality of A + cardinality of B. This means: a) A is a subset of B b) B is a subset of A c) A and B are disjoint d) None of the mentioned

c

Step-by-step explanation:

a) is wrong.

If A is a subset of B, then cardinality of (AUB) = cardinality B.

For example: A = {1}, B = {1,2,3} cardinality (A) = 1, cardinality (B) = 3.

AUB = {1,2,3} cardinality (AUB) = 3 = cardinality (B)

For the same reason as a), b) is wrong. If B is a subset of A, then the cardinality (AUB) = cardinality (A).

c) is right.

We have already seen that if a set A is a subset of a set B, then cardinality (AUB) = B.

Using A = {1} and B = {2,3}, cardinality (A) = 1, cardinality (B) = 2

Then AUB = {1,2,3} and cardinality (AUB) = 3 = cardinality (A) + cardinality (B)