Option 1 states that the weight of a body is different on different planets. This is correct because weight is the force of gravity acting on an object, and gravity varies from planet to planet.

Option 2 states that the mass of a body on the earth, moon, and in empty space is the same. This is also correct because mass is a measure of the amount of matter in an object, and it does not change based on location.

Option 3 states that weightlessness occurs when the gravitational forces acting on a body are counter-balanced. This is also correct because weightlessness is the absence of a net force due to gravity, which can occur in situations like freefall or in orbit around the Earth.

Option 4 states that weight and mass of a body are equal at sea level on the surface of the earth. This statement is incorrect. Weight and mass are different physical quantities - mass is a measure of the amount of matter in an object, while weight is the force exerted on that object by gravity. Weight depends on the mass and the strength of the gravitational field, so it will vary depending on location and altitude.

Alert - correct answer should be: Option 4 is incorrect.