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

Match each of the set on the left described in the roster form with the same set on the right described in the set-builder form:

$(i) \{ P,R,I,N,C,A,L\} $	$(a) \{ x:x \text{ is a positive integer and is a divisor of } 18\} $
$(ii) \{ 0\} $	$(b) \{ x:x \text{ is an integer and } x^2 - 9 = 0\} $
$(iii) \{ 1,2,3,6,9,18\} $	$(c) \{ x:x \text{ is an integer and } x + 1 = 1\} $
$(iv) \{ 3, -3\} $	$(d) \{ x:x \text{ is a letter of the word } PRINCIPAL\} $

If $A$ and $B$ are two sets,then $A \cup (A \cap B)$ is equal to

Two dice are thrown. The events $A$,$B$,and $C$ are as follows:
$A$: getting an even number on the first die.
$B$: getting an odd number on the first die.
$C$: getting the sum of the numbers on the dice $\leq 5$.
State true or false: (give reason for your answer)
Statement: $A$ and $B^{\prime}$ are mutually exclusive.

Which of the following are sets? Justify your answer.
The collection of all natural numbers less than $100$.

The collection of intelligent students in a class is: