Match each of the Maclaurin series with the function it represents.

1. $\displaystyle \sum_{n=0}^\infty (-1)^n \frac{x^{2n+1}}{(2n+1)!}$

2. $\displaystyle \sum_{n=0}^\infty \frac{(-1)^n x^{2n+1}}{2n+1}$

3. $\displaystyle \sum_{n=0}^\infty \frac{(-1)^n x^{2n}}{(2n)!}$

4. $\displaystyle \sum_{n=0}^\infty \frac{x^n}{n!}$

A. $\sin(x)$
B. $e^x$
C. $\arctan(x)$
D. $\cos(x)$