Answer: D - Lipids
Lipids provide a long term energy storage because they contain longer C-H bonds compared to the other organic molecules, making it easier for them to store larger amount of energy. Moreover, upon burning they produce twice the amount of calories compared to that of the carbohydrates.
There are sometimes similarities in the embryonic stages of organisms that do not exist in the adult stages.
I believe it is the first option
Decaying uranium atoms in the earth's crust result in Radon gas. Radon gas cannot be synthetically or commercially produced. It is produced as the result of the natural breakdown of uranium i.e. decaying uranium atoms. Radon gas is a naturally occurring radioactive gas. People are exposed to Radon gas via the inhalation and ingestion of the gas. Because it is found in the ground, water or building materials, Radon gas can enter work buildings as well as private dwellings.
