Write the Expression for the General (Or Nth)termrm $\mathbf { a } _ { \mathbf { n } } ,$

Multiple Choice

Write the expression for the general (or nth) termrm, $\mathbf { a } _ { \mathbf { n } } ,$ , of the geometric sequence.
-3, 9, 27, 81, 243,. . .

A) $a _ { n } = 3 ^ { n }$
B) $a _ { n } = 3 ^ { n - 1 } + 3$
C) $a _ { n } = 6 n$
D) $a _ { n } = 3 + 6 ( n - 1 )$