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

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

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