Answer:

Introduction:
In a sedimentation tank, the process of settling solids occurs due to the difference in density between the solid particles and the fluid. Sedimentation speed refers to the rate at which these solid particles settle to the bottom of the tank under the influence of gravity.

Effect of Temperature:
The temperature of the fluid in a sedimentation tank can have a significant effect on the sedimentation speed. When the temperature is increased, the sedimentation speed also increases.

Explanation:

1. Viscosity:
The viscosity of a fluid is a measure of its resistance to flow. It is influenced by temperature, whereby an increase in temperature leads to a decrease in viscosity. In the case of sedimentation tanks, the fluid is usually water, and as the temperature increases, the viscosity of water decreases.

2. Stoke's Law:
Stoke's Law is a fundamental equation that describes the settling behavior of particles in a fluid. According to Stoke's Law, the sedimentation speed is directly proportional to the difference in density between the solid particles and the fluid, and inversely proportional to the viscosity of the fluid.

3. Decreased Viscosity:
When the temperature of the sedimentation tank is increased, the viscosity of the fluid decreases. This reduction in viscosity results in a decrease in the resistance to flow, allowing the solid particles to settle more easily and quickly.

4. Increased Sedimentation Speed:
As the viscosity decreases, the sedimentation speed increases due to the reduced resistance to settling. The solid particles are able to move more freely through the fluid, allowing them to settle to the bottom of the tank at a faster rate.

Conclusion:
In summary, when the temperature of a sedimentation tank is increased, the viscosity of the fluid decreases. This decrease in viscosity leads to a decrease in resistance to settling, resulting in an increased sedimentation speed. Therefore, the correct answer is option 'A' - the sedimentation speed gets increased.