The correct option is C 2
Let us consider an arbitary singleton set, say A={a}.
Since every set is a subset of itself and empty set is a subset of every set, we have ϕ and A to be subsets of A.
Also, these are the only subsets of A.
Thus, Power set of A, P(A)={ϕ,A}
⟹n(P(A))=2