Which of the following sets is finite or infinite?
The set of prime numbers less than $99$.

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

Make correct statements by filling in the symbols $\subset$ or $\not\subset$ in the blank spaces:
${ x:x \text{ is an equilateral triangle in a plane} } \dots { x:x \text{ is a triangle in the same plane} }$

In the following,state whether $A=B$ or not:
$A=\{a, b, c, d\} ; B=\{d, c, b, a\}$

If $A = \{1, 2, 3, 4, 5\}$, then which of the following statements is not true?

If ${N_a} = \{an : n \in N\}$,then ${N_3} \cap {N_4} = $