In primary sedimentation, the 0.2 mm inorganic solids get separated if specific gravity is A. 2.25 B. 2.50 C. 2.55 D. 2.65

The correct answer is B. 2.50.

The specific gravity of a substance is its density relative to the density of water. The density of water is 1 g/mL. A substance with a specific gravity of 2.50 is 2.5 times as dense as water.

In primary sedimentation, the 0.2 mm inorganic solids get separated from the water if the specific gravity of the solids is greater than the specific gravity of the water. This is because the heavier solids will sink to the bottom of the tank, while the lighter water will float on top.

The specific gravity of the solids is 2.50. The specific gravity of the water is 1.00. Therefore, the solids will sink to the bottom of the tank and be separated from the water.

The other options are incorrect because they are not greater than the specific gravity of water.

A. 2.25 is less than the specific gravity of water.
C. 2.55 is equal to the specific gravity of water.
D. 2.65 is greater than the specific gravity of water, but it is not close enough to 2.50 to ensure that the solids will sink to the bottom of the tank.