First, you have to know what the set P(A) is. This is a set. It has n(A) elements, and each element is a small set (each of these small sets is a proper subset of the original set A), that is to say, it is a set of elements and a "set". Here, P and N are rules, and A stands for the set we usually understand.

Then 1 is obviously correct. At this time, a represents a small element in the set P(A).

2 is wrong, where the number of subsets of P(A) is equal to the n power of 2, so the number of elements cannot be 3.

3 is wrong, because for any power set, an empty set is its proper subset, so P(A)∩P(B) has at least one element? , should be expressed as P(A)∩P(B)={? }, here? Represents an empty set, {? } stands for one? Is a small collection of elements.

4 is correct, you understand the last one, this one is easy to understand.

5 is correct, that is to say, the number of elements in two sets is different by 1, so how much is the number of elements in their power sets, that is, how much is the number of subsets? I don't know if your teacher has summed it up for you. The number of subsets is equal to the n power of 2. Just bring it in and calculate it.