Find an Explicit Rule for the Nth Term of the Sequence

Multiple Choice

Find an explicit rule for the nth term of the sequence.
- $4,12,36,108 , \ldots$

A) $a _ { n } = 3 \cdot 4 ^ { n - 1 }$
B) $a _ { n } = 4 \cdot 3 ^ { n }$
C) $a _ { n } = 4 \cdot 3 ^ { n - 1 }$
D) $a _ { n } = 4 \cdot 3 ^ { n + 1 }$