Earth is not a perfect sphere. Due to the ______ gravitational pull, Earth bulges out on the sides closest to and farthest from
the Moon. This distorting pull is known as a tidal force, and it is responsible for the changes in water levels that are called
high and low tides.
Moon’s
Moons
Moons’
Moon
Choice A is the best answer. The convention being tested is the use of possessive nouns. The singular possessive noun
"Moon’s" correctly indicates that there is only one Moon, and it has a gravitational pull.
Choice B is incorrect because the context requires the singular possessive noun "Moon’s," not the plural noun "Moons."
Choice C is incorrect because the context requires the singular possessive noun "Moon’s," not the plural possessive noun
"Moons’." Choice D is incorrect because the context requires the singular possessive noun "Moon’s," not the singular noun
"Moon."