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. $4,-10,25,-\frac{125}{2}, \ldots$

A) $a_{n}=2\left(-\frac{5}{2}\right) ^{n-1}$
B) $a_{n}=2\left(-\frac{5}{2}\right) ^{n-2}$
C) $a_{n}=4\left(-\frac{5}{2}\right) ^{n-1}$
D) $a_{n}=-2\left(-\frac{5}{2}\right) ^{n}$
E) $a_{n}=-4\left(-\frac{5}{2}\right) ^{n}$