Write an Expression for the N Th Term of the Sequence

Multiple Choice

Write an expression for the n th term of the sequence $\frac { 1 } { 6 } , - \frac { 1 } { 36 } , \frac { 1 } { 216 } , - \frac { 1 } { 1296 } , \ldots$ Assume that n begins with 1.

A) $a _ { n } = \frac { ( - 1 ) ^ { n } } { 6 ^ { n + 2 } }$
B) $a _ { n } = \frac { ( - 1 ) ^ { n + 1 } } { 6 ^ { n + 1 } }$
C) $a _ { n } = \frac { ( - 1 ) ^ { n } } { 6 ^ { n + 1 } }$
D) $a _ { n } = \frac { ( - 1 ) ^ { n + 1 } } { 6 ^ { n } }$
E) $a _ { n } = \frac { ( - 1 ) ^ { n } } { 6 ^ { n } }$