ANS:A - 5

The specific gravity of a substance is defined as the ratio of its density to the density of water. When an object is submerged in water, it experiences a buoyant force that is equal to the weight of the water displaced by the object. Therefore, the difference in weight between the object in air and when submerged in water is equal to the weight of the water displaced by the object. Given that the object weighs 5 kg in air and 4 kg when submerged in water, the weight of the water displaced by the object is 5 kg - 4 kg = 1 kg. Since 1 liter of water has a mass of 1 kg, the volume of water displaced by the object is 1 liter. Therefore, the volume of the object is also 1 liter. Now, the specific gravity (SG) of a substance is defined as the ratio of its density to the density of water. Since the volume of the object is 1 liter and its weight in air is 5 kg, its density is 5 kg/L. The density of water is 1 kg/L. Therefore, the specific gravity of the object is: SG = Density of object / Density of water = 5 kg/L / 1 kg/L = 5. So, the specific gravity of the metal is 5.