If a body is allowed to fall down a height freely, its speed increases continuously. It is because

Options

A. air does not exert frictional force
B. magnetic force of earth increases its speed
C. gravitational force of earth increases its speed
D. pressure of air forces it downward.

Explanation

To solve the question, "If a body is allowed to fall down a height freely, its speed increases continuously. It is because," we need to analyze the options provided and understand the underlying physics principles.

### Step-by-Step Solution:

1. **Understanding Free Fall**: When a body is in free fall, it is only influenced by gravity (assuming air resistance is negligible). This means that the only force acting on it is the gravitational force exerted by the Earth.

2. **Identifying the Forces**: The options provided are:
- A) Air does not exert frictional force.
- B) Magnetic force of Earth increases its speed.
- C) Gravitational force of Earth increases its speed.
- D) Pressure of air forces it downwards.

3. **Analyzing Each Option**:
- **Option A**: While it's true that air resistance is minimal in free fall, this does not explain why speed increases. The absence of air resistance allows for acceleration due to gravity, but it is not the primary reason for the increase in speed.
- **Option B**: The magnetic force of Earth does not play a significant role in the motion of falling bodies. This option is incorrect.
- **Option C**: The gravitational force of the Earth acts on the body and causes it to accelerate towards the ground. According to Newton's second law (F = ma), the gravitational force results in an increase in speed as the body falls.
- **Option D**: The pressure of air does not push the body downwards; instead, it can create resistance. This option is also incorrect.

4. **Conclusion**: The correct answer is **Option C**: "Gravitational force of Earth increases its speed." This is because the gravitational force causes the body to accelerate, leading to an increase in its velocity as it falls.

### Final Answer:
The speed of a body in free fall increases continuously because the gravitational force of the Earth increases its speed.