Tides on earth are caused primarily by
a. the moon’s gravitational force.
c. earth’s landscape.
b. the sun’s gravitational force.
d. jupiter’s gravitational force.

(A) The moon’s gravitational force.

Explanation:

The tides are refers to the periodic fall and rise in the level of the water in ocean and it is primarily caused by the gravitational force of attraction of the moon in the different part of the earth. The tide are also caused by the sun's gravitational force of attraction but it is the secondary reason or cause.

 The moon has the greatest effect as the moon is smaller as compared to the sun so that is why the moon's gravitational force of attraction is the main caused.

Therefore, Option (A) is correct.