Question

According to the universal law of gravitation _____.

Answer 1

The correct answer is:

a. everything has a gravitation force because everything has mass

In fact, the universal law of gravitation states that every object with mass M exerts an attractive, gravitational force to any other object with mass m, and the size of this force is given by:

$F=G\frac{Mm}{r^2}$

where G is the gravitational constant, and r is the distance between the two objects.

Answer 2

According to the universal law of gravitation, all particles attract every other particle with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. So the answer here would be, 

a. everything has a gravitational force because everything has mass.