Atoms and elements are examples of A. molecules. B. mixtures. C. compounds. D. pure substances.

b..

is the correct one

explanation:

covalent bonds form as valence electrons are shared between two atoms. lewis structures and structural formulas are common ways of showing the covalent bonding in organic molecules. formal charge describes the changes in the number of valence electrons as an atom becomes bonded into a molecule.

the leaf is an organ of a typical plant, and the main functions are to complete photosynthesis and allow the plant to exchange gas, just like how we have the respiratory system. leaves have the stomata, which collects maintains co2 and o2 levels. this is necessary for cell metabolism. the leaf also collects sunlight using chloroplasts. succinctly, leaves own a pivotal role in sustaining plant life.