The correct answer is A. The moon's gravity pushes on the earth. The push indents the earth's watery envelope and creates tidal bulges. Where the water is pushed in is high tide. There are two types of tides on Earth - high tide and low tide. Both of these types of tides are affected by the Earth's natural satellite, the Moon. Due to its gravity, everything on Earth is pushed, however, waters on Earth are under the strongest impact by this.