Answer:
1 element
Step-by-step explanation:
Call B a set of n elements.
We can say that B is a subset of A if each element of B is also in A. This is written as:
B ⊆A
If a Set B contains all the elements of A, we can also say that B is a subset of A, where B = A.
Therefore, if set A has four elements, then for B to be a subset of A, the number of elements in B must be less than or equal to 4 but greater than 0. {1, 2, 3, 4}
Finally, according to the definition, B must have at least 1 element of A
