Choose the wrong option.

1. Inertial mass is a measure of the difficulty of accelerating a body by an external force whereas gravitational mass is relevant in determining the gravitational force on it by an external mass.
2. That the gravitational mass and inertial mass are equal is an experimental result.
3. That the acceleration due to gravity on the earth is the same for all bodies is due to the equality of gravitational mass and inertial mass.
4. Gravitational mass of a particle-like proton can depend on the presence of neighbouring heavy objects but the inertial mass cannot.

Hint: The gravitational mass of a body is equivalent to its inertial mass.
Explanation:
The gravitational mass of a proton is equivalent to its inertial mass and is independent of the presence of neighbouring heavy objects.