Horizontal pressure gradient force:

a depends only on the difference in pressure between two locations
b is independent of distance
c has both a magnitude and direction associated with it
d only affects air that is already in motion

C has both a magnitude and direction associated with it

Explanation:

Horizontal pressure gradient  -

It is one of the important and main forces which act on the air to make it move like a wind .

The pressure gradient force points from the high towards the lower pressure zone , it is oriented in the direction opposite from that of the pressure gradient .

Hence , the correct option for the Horizontal pressure gradient force is ( c ) .