Two sphere of masses `m` and `M` are situated in air and the gravitational force between them is `F`. The space around the masses in now filled with a liquid of specific gravity `3`. The gravitational force will now be

Options

A. `F/9`
B. `3F`
C. `F`
D. `F/3`

Explanation

To solve the problem, we need to analyze how the gravitational force between two masses is affected by the medium surrounding them.

### Step-by-Step Solution:

1. **Understanding Gravitational Force**:
The gravitational force \( F \) between two masses \( m \) and \( M \) separated by a distance \( r \) in a vacuum or air is given by Newton's law of gravitation:
\[ F = \frac{G \cdot m \cdot M}{r^2} \]
where \( G \) is the gravitational constant.

2. **Effect of Medium**:
The problem states that the space around the masses is filled with a liquid of specific gravity 3. Specific gravity is a measure of the density of a substance compared to the density of water. Since the specific gravity of the liquid is 3, its density \( \rho \) can be expressed as:
\[ \rho = 3 \cdot \rho_{\text{water}} = 3 \cdot 1000 \, \text{kg/m}^3 = 3000 \, \text{kg/m}^3 \]
However, it is important to note that the gravitational force between two masses does not depend on the medium in which they are placed.

3. **Conclusion**:
Since the gravitational force is independent of the surrounding medium (whether it is air, liquid, or solid), the gravitational force \( F \) between the two spheres will remain the same even when the space around them is filled with the liquid. Therefore, the gravitational force will still be:
\[ F = \frac{G \cdot m \cdot M}{r^2} \]

### Final Answer:
The gravitational force will remain \( F \).