An action potential is (chemical or electrical) in nature. The neuron is more (- or +) inside because of negatively charged molecules like on the inside and cations like outside. As the neuron fires, there’s a temporary reversal in as the axon undergoes (depolarization or repolarization) as flow into the cell. The action potential travels down the , sending a signal down it. The whole thing takes about 1/1,000th of a .

Option D, Concrete and water are not minerals

Explanation:

Mineral is a substance than is naturally occurring in the environment and comprises of following other characteristics –  

a)Inorganic nature

b)It must have a definite chemical composition  

c)It must have ordered internal structure

Naturally occurring substance cannot be made artificially. For example – steel, concrete are not minerals. However, water is naturally occurring but it is not inorganic in nature.  

Hence, option D is correct