Which of the followings about item and itemset is true?

A$.$ a frequent itemset contains $1$ frequent item only

B$.$ frequent $3-$itemset $\{$B$,$ G$,$ R$\}$ contains $3$ frequent items

C$.$ frequent $4-$itemset $\{$B$,$ G$,$ R$,$ Z$\}$ contains $14$ frequent k$-$itemsets for k$=1$ to $4$

D$.$ None of the above