Question

How many elements does A=0 have ?

Answer 1

$P(A)$ is the power set of set $A.$

Number of elements of $P(A)=2^n,$ where $n$ is the number of elements of the set $A.$

Given $A=\empty,$ then the number of elements of set $A=0.$

Number of elements of $P(A)=2^n=2^0=1.$

Hence $P(A)$ has one element.