15. which excretory organ eliminates water and some chemical wastes in perspiration?

I think the answer is skin. Skin contains sweat glands which secrete a fluid waste called sweat or perspiration; nonetheless, its primary functions are temperature control and release of pheromone. Its role as a part of the excretory is therefore minimal. Additionally, sweating also maintains the levels of salt in the body.

They include lobsters and crabs

The answer is joseph is observing the colour of the reaction mixture to see whether proteins are present in the given solution.