Which of the following sets is a subset of all other sets?

Consider the experiment of rolling a die. Let $A$ be the event 'getting a prime number' and $B$ be the event 'getting an odd number'. Write the sets representing the events $A$ and $B$.

If $A = \{x \mid x \text{ is a prime number, } 0 \leq x \leq 9\}$,then the number of elements of the power set of $A$ is

Write the following interval in set-builder form: $(6, 12]$

The number of subgroups of the group $(Z_{5}, +_{5})$ is

Write the set $\{ x : x \text{ is a positive integer and } x^2 < 40 \}$ in the roster form.