Vectors $\overrightarrow { \mathbf { M } }$ And $\overrightarrow { \mathrm { N } }$

Vectors $\overrightarrow { \mathbf { M } }$ and $\overrightarrow { \mathrm { N } }$ obey the equation $\overrightarrow { \mathbf { M } }$ + $\overrightarrow { \mathrm { N } }$ = 0. These vectors satisfy which one of the following statements?

A) Vectors $\overrightarrow { \mathbf { M } }$ and $\overrightarrow { \mathrm { N } }$ are at right angles to each other.
B) Vectors $\overrightarrow { \mathbf { M } }$ and $\overrightarrow { \mathrm { N } }$ point in the same direction.
C) Vectors $\overrightarrow { \mathbf { M } }$ and $\overrightarrow { \mathrm { N } }$ have the same magnitudes.
D) The magnitude of $\overrightarrow { \mathbf { M } }$ is the negative of the magnitude of $\overrightarrow { \mathrm { N } }$ .