Yes they did. It is generally known that amphibians breathe through their skin.
Axon: the messenger cell that carries the command to contract muscles.
Answer:
Zinc. (Ans. B)
Explanation:
Trace minerals: Trace minerals are defined as the inorganic molecules which are necessary for the human body for the different functions.
Zinc function in human metabolism is defined as a cofactor for numerous enzymes. Zinc play a role as a catalyst in a broad range of reactions. It is involved in the metabolic pathway directly or indirectly with lipids, carbohydrates, proteins, energy metabolism, and they are also important for the cell division process.
They also need for tissue and growth repair, and for reproductive development also. It's also played a vital role in immune system such as wound healing or required for the function and structure of the skin.