Which bond is weak covalent or hydrogen?

Hydrogen

Explanation:

They have energies of 1–3 kcal mol-1 (4–13 kJ mol-1) compared with approximately 100 kcal mol-1 (418 kJ mol-1) for a carbon-hydrogen covalent bond.

i would say the prokaryotic cells the prokaryotic cells are less complex, are usually found only in unicellular organisms and have more limited capabilities than eukaryotic cells.

well, that's easy; the answer's c, "it reduces contamination of the water and substrate of the estuary."