How many elements does $P(A)$ have,if $A = \varnothing$?

Let $A = \{1, 2, 3, 4, 5, 6\}$. Insert the appropriate symbol $\in$ or $\notin$ in the blank space:
$2 \dots A$

Which of the following pairs of sets are disjoint?
$A = \{ x : x \text{ is an even integer} \}$
$B = \{ x : x \text{ is an odd integer} \}$

Write down all the subsets of the following set: $\emptyset $

State which of the following sets are finite or infinite:
$\{ x : x \in N \text{ and } x \text{ is odd} \}$

Given the sets $A = \{1, 3, 5\}$,$B = \{2, 4, 6\}$ and $C = \{0, 2, 4, 6, 8\}$,which of the following may be considered as a universal set for all the three sets $A$,$B$ and $C$?
$X = \{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10\}$