If a ⊂ b, b may have more elements than a. true false

That's true. If A is a subset of B, it means that every element in A is also an element in B. This means that B has, at least, as many elements as A. Nothing prevents B from having more elements though, which don't belong to A.

Consider this example:

A is a subset of B, because every element of A (1,2,3,4) is also an element of B (1,2,3,4 are in B as well).

Still, B has two more elements (5,6) which don't belong to A, so a superset can have (and typically does actually) more elements than its subset.

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step-by-step explanation: