The value of g decreases inside the surface of Earth because

Options

A. A force of upward attraction is applied by the shell of Earth above
B. The shell of Earth above exerts no net force
C. The distance from the centre of the Earth decreases
D. The density of the material at the centre of the Earth is very small

Explanation

To solve the question, "The value of g decreases inside the surface of Earth because," we need to analyze the options provided and understand the physics behind gravitational acceleration inside the Earth.

### Step-by-Step Solution:

1. **Understanding Gravitational Acceleration (g)**:
- The gravitational acceleration (g) at any point is determined by the mass of the Earth and the distance from the center of the Earth. The formula for gravitational acceleration at a distance r from the center of the Earth is given by:
\[ g' = \frac{GM}{r^2} \]
- Here, G is the gravitational constant, M is the mass enclosed within radius r, and r is the distance from the center of the Earth.

2. **Behavior Inside the Earth**:
- Inside the Earth, as you go deeper (i.e., as you decrease the distance from the center), the effective mass that contributes to gravitational attraction changes.
- According to the shell theorem, the gravitational force inside a uniform spherical shell of mass is zero. Therefore, only the mass that is at a radius less than r contributes to the gravitational force at that point.

3. **Distance from the Center**:
- As you move towards the center of the Earth, the distance (r) from the center decreases. Since gravitational acceleration is inversely proportional to the square of the distance from the center, a decrease in r leads to a decrease in g.

4. **Conclusion**:
- The value of g decreases inside the surface of the Earth primarily because the distance from the center of the Earth decreases. This is the correct reason as it directly affects the gravitational force experienced at that point.

### Final Answer:
The value of g decreases inside the surface of Earth because the distance from the center of the Earth decreases.