The regular rise and fall of sea level known as tides are caused primarily by which of the following gravitational effects on the Earth?

Introduction / Context:
Tides are one of the most visible and important oceanographic phenomena, affecting navigation, fishing, coastal ecosystems, and human activities. Understanding the main cause of tides is a basic concept in physics and geography. This question asks you to identify which celestial body's gravitational pull is primarily responsible for tidal patterns on Earth.

Given Data / Assumptions:

• The question describes tides as sea level changes.
• Options include atmospheric effects, gravitational effects of Venus, the Sun, and the Moon.
• We assume standard textbook explanation of tides using gravitational forces.

Concept / Approach:
The Moon exerts a gravitational pull on Earth, and this attraction is strongest on the side of Earth closest to the Moon and weakest on the opposite side. This difference in gravitational force, called tidal force, causes two tidal bulges: one on the near side and one on the far side of Earth. As Earth rotates, coastal areas move in and out of these bulges, producing high and low tides. The Sun also contributes to tides, but its effect is less than that of the Moon, because the change in gravitational pull across Earth's diameter is smaller due to the Sun's great distance. Venus has a negligible tidal effect on Earth, and atmospheric effects do not directly create the basic tidal cycle.

Step-by-Step Solution:
Step 1: Recall that tides are explained using gravitational attraction between Earth and celestial bodies.Step 2: Recognise that the Moon is much closer to Earth than the Sun, so the difference in its gravitational pull across Earth is larger.Step 3: Understand that this difference produces tidal bulges on the side facing the Moon and the side opposite it.Step 4: Note that as Earth rotates through these bulges, coastal areas experience rising and falling sea levels.Step 5: Conclude that the Moon's gravitational effect is the primary cause of tides, with the Sun playing a secondary role.

Verification / Alternative check:
Standard diagrams in geography and physics textbooks show Earth, Moon, and Sun positions during spring tides and neap tides. In all these explanations, the Moon is identified as the main tidal force, with the Sun modifying tidal range. No serious source attributes primary tidal generation to atmospheric effects or to the gravity of distant planets such as Venus.

Why Other Options Are Wrong:
The atmospheric effect of Earth influences waves, currents, and weather, but not the basic astronomical tidal cycle. The Sun does contribute to tides, but the question asks for the primary cause, which is the Moon. Venus is a planet much farther from Earth than the Moon and has no significant tidal influence here. Thus, only the gravitational effect of the Moon on Earth correctly explains the main cause of tides.

Common Pitfalls:
Some learners remember that both the Sun and the Moon affect tides and may mistakenly pick the Sun. Others may think that winds and atmospheric pressure changes alone create tides, confusing them with storm surges or waves. Keeping in mind that ordinary daily tides are astronomical in origin and mainly controlled by the Moon helps avoid such errors.

Final Answer:
The tides in the sea are primarily due to the gravitational effect of the Moon on the Earth.