Respuesta :

Answer:

A⊆B

Step-by-step explanation:

C⊆D if the set C contains only elements from set D.

Let's look at the first choice:

B⊆A is not true because 3 and 4 are not in A.

Second choice:

3⊆A is not true because 3 is not a set; it is an element.

Also, 3 is not even in {1,2}.

Third choice:

See explanation for choice 2.

Fourth choice:

A⊆B is true because all the elements in A are contained in B.

That is the elements 1 and 2 are contained in the set {1,2,3,4} which is B.

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