单项选择题

The term "tides" has come to represent the cyclical rising and failing of ocean waters, most notably evident along the shoreline as the border between land and sea moves in and out with the passing of the day. The primary reason for this constant redefinition of the boundaries of the sea is the gravitational force of the moon.
This force of lunar gravity is not as strong as Earth’s own gravitational pull, which keeps our bodies and our homes from being pulled off the ground, through the sky, and into space toward the moon. It is a strong enough force, however, to exert a certain gravitational pull as the moon passes over Earth’s surface. This pull causes the water level to rise(as the water is literally pulled, ever so slightly, toward the moon) in those parts of the ocean that are exposed to the moon and its gravitational forces. When the water level in one part of the ocean rises, it must naturally fall in another, and this is what causes water levels to change, dramatically at times, along any given piece of coastline.

The word "lunar" in the first sentence of paragraph2 most nearly means （）.