Q1: The sensitiveness of a level tube decreases if

ANS:D - both viscosity and surface tension are increased.

I think due to increase in viscosity and surface tension, the length of the bubble decreases (as the liquid tends to become more spherical shape). Since the length of bubble decreases, the sensitivity also decreases. So, option D is correct. If surface tention decrease with rise of temperature, and viscosity decrease with rise temperature then why sensitivity of bubble tube get decrease whether it's inversely proportional to viscosity and surface tention? Sensitivity is L/R which means it is directly proportional to the length and inversely proportional to the radius of curvature soo A is the correct answer.

Option D is completely wrong as they are directly proportional to sensitivity. Right option is D because we know sensitiveness is also increased by the increase in the length of the bubble and by a decrease of viscosity and surface tension of the liquid in the level tube ref.

Book C. L Kochher page 261.