Question

Planets orbit the Sun because _____.

Answer 1

This is a poorly written question.

Out of the choices listed, the first one is the only one that includes
a true statement ... the greater the mass of two objects, the greater
the gravitational attraction is between them. 

-- Newton's law of universal gravitation doesn't "suggest" that.  It states it ...
boldly and unequivocally.

-- The law doesn't refer to the "greatness" of the mass of the two objects. 
It refers to the product of their masses.

-- It's true that the law of universal gravitation can be massaged and
manipulated to reveal the existence of gravitational planetary orbits.
But there's a lot more to it than simply the masses.

For example ... the gravitational force between two objects is inversely
proportional to
                           (the distance between the objects)² .

It turns out that IF that exponent were not precisely, exactly  2.000000... ,
then gravitational orbits could not exist.