Answer:
1: Cobalt Chloride paper is used for testing for water leaks or high humidity. Moisture turns the paper light pink/white. Useful in difficult to reach places and recesses. Responsive to 50% relative humidity and above, and any direct measure of an aqueous solution.
2: It is because this paper turns into a pink colour when it reacts with water.
3: During transpiration, the leaves lose more water from their upper surface.