Question

b. empty set is element of empty set
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Answer 1

Answer:

Yes

The empty set is a subset of EVERY set. (Because the empty set has no elements so all zero of its elements are in every other set. ... The element doesn't have any elements not in B so empty set $\subset B and it doesn't matter what B is.

Answer 2

Answer:

This is also a null set { }

And you are correct