Find a Formula for the N Th Term of the Geometric

Multiple Choice

Find a formula for the n th term of the geometric sequence. Assume that n begins with 1. $a_{1}=3, r=\frac{7}{4}$

A) $a_{n}=3\left(\frac{7}{4}\right) ^{n-1}$
B) $a_{n}=\left(\frac{21}{4}\right) ^{n-1}$
C) $a_{n}=\left(\frac{7}{4}\right) ^{n}$
D) $a_{n}=\left(\frac{21}{4}\right) ^{n}$
E) $a_{n}=3\left(\frac{7}{4}\right) ^{n}$