Select the First Five Terms of the Sequence Defined Recursively $$a _ { 1 } = 9 , a _ { k + 1 } = a _ { k } + 3$$

Select the first five terms of the sequence defined recursively.Use the pattern to write the nth term of the sequence as a function of n.(Assume that n begins with 1. ) ​ $$a _ { 1 } = 9 , a _ { k + 1 } = a _ { k } + 3$$ ​

A) $\begin{array} { l } 9,12,15,18,21 \\a _ { n } = 3 n + 3\end{array}$
B) $\begin{array} { l } 9,12,15,18,21 \\a _ { n } = 6 n + 3\end{array}$
C) $\begin{array} { l } 9,12,15,18,21 \\a _ { n } = 3 n + 6\end{array}$
D) $\begin{array} { l } 9,12,15,18,21 \\a _ { n } = 6 n - 3\end{array}$
E) $\begin{array} { l } 9,12,15,18,21 \\a _ { n } = 3 n - 6\end{array}$