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Which of the following statements about relatively compact subsets is(are) true?

If $A\subset B$ are two subsets, $B$ is relatively compact, then $A$ is relatively compact.

If $X$ is Hausdorff, $A\subset B$ are two subsets, $B$ is relatively compact, then $A$ is relatively compact.

The intersection of two relatively compact subsets is relatively compact.

The union of two relatively compact subsets is relatively compact.

There are topological spaces that are not homeomorphic to any relatively compact subspace.