The regular rise and fall of sea level is called a tide. Which term describes this daily phenomenon?

• A. Eclipse
• B. Rotation
• C. Tide
• D. Orbit

Answer: (C)

The concept being tested is recognizing terms for regular changes in Earth's oceans. The regular rise and fall of sea level is caused by the gravitational pull of the Moon (and the Sun) on Earth's oceans, which creates bulges. As the Earth rotates, coastlines move into and out of these bulges, producing high tides and low tides on a daily cycle. The term that describes this regular, daily phenomenon is tide.

The other options describe different things: an eclipse is when celestial bodies align to obscure one another; rotation is the spinning of Earth on its axis; orbit is the path a body takes as it travels around another. These don’t describe the daily rise and fall of sea level, so tide is the correct term.