Which Venn diagram represents the truth of the statement "Some teenagers are not dreamers"?

If $A = \{3, 6, 9, 12, 15, 18, 21\}$,$B = \{4, 8, 12, 16, 20\}$,$C = \{2, 4, 6, 8, 10, 12, 14, 16\}$,and $D = \{5, 10, 15, 20\}$,find $C - A$.

If $A$ and $B$ are two sets such that $n(A) = 0.16$,$n(B) = 0.14$,and $n(A \cup B) = 0.25$,then $n(A \cap B)$ is equal to:

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 set representing the event '$A$ or $B$'.

Which of the following pairs of sets are disjoint?
$A = \{a, e, i, o, u\}$ and $B = \{c, d, e, f\}$

If $A = \{ x : x \text{ is a natural number} \}$,$B = \{ x : x \text{ is an even natural number} \}$,$C = \{ x : x \text{ is an odd natural number} \}$,and $D = \{ x : x \text{ is a prime number} \}$,find $A \cap C$.