If $A = \{3, 5, 7, 9, 11\}$,$B = \{7, 9, 11, 13\}$,$C = \{11, 13, 15\}$ and $D = \{15, 17\}$; find $B \cap C$.

Find the union of each of the following pairs of sets: $A = \{a, e, i, o, u\}$,$B = \{a, b, c\}$.

If $A=\{1, 2, 3, 4\}, B=\{3, 4, 5, 6\}, C=\{5, 6, 7, 8\}$ and $D=\{7, 8, 9, 10\}$,find $A \cup C$.

Let $A$ and $B$ be subsets of a set $X$. Then,

If $A = \{3, 5, 7, 9, 11\}$,$B = \{7, 9, 11, 13\}$,$C = \{11, 13, 15\}$,and $D = \{15, 17\}$,find $A \cap D$.

Which Venn diagram represents the truth of the statement "All students are hard working."
Where $U$ = Universal set of human beings,$S$ = Set of all students,$H$ = Set of all hard workers.