Answer: The answers are the first and third options.
Cells are considered one of the characteristics of life because all living things are made of cells
The number of protons is equal to the atomic number of every element in the periodic table.
Example: The atomic number of Niobium (Nb) is 41. Therefore, the number of protons is also 41.
A. Mixture and D. Compound
Covalent bond is formed when they share the free electrons in such a way that both of them fill their octet and gain stability.