Which of the following is a set? Justify your answer.
The collection of all boys in your class.

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 $C$?
$X = \{0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10\}$

Determine whether the following set is finite or infinite:
$\{1, 2, 3, \ldots\}$

Write the following as an interval: $\{ x : x \in R, -4 < x \le 6 \}$

Let $A, B, C$ be subsets of a set $X$. Which of the following set-theoretic statements is valid?

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