Arrow A is showing the wrong direction of the gravitational force.
The direction of the gravitational force is along the line connecting the centers of the Earth and the Moon. This gravitational force is what keeps the Moon in orbit around the Earth.
Looking at the diagram, arrows B, C, and D are pointing towards the center of the moon, indicating that the forces are directed towards the center of the moon.
On the contrary, arrow A is pointing in a direction that is not the center of the moon. In other words, arrow A is pointing in the wrong direction.
There is not enough information in the diagram to comment on the magnitude of the gravitational force.