Four Particles, Each with Mass M, Are Arranged Symmetrically About $\uparrow$

Multiple Choice

Four particles, each with mass m, are arranged symmetrically about the origin on the x axis.A fifth particle, with mass M, is on the y axis.The direction of the gravitational force on M is:

A) " $\uparrow$ "
B) " $\downarrow$ "
C) " $\leftarrow$ "
D) " $\rightarrow$ "
E) "none of these directions"