Name and describe the four types of aquatic organisms

Plz ! ive been stuck on this forever

Which best describes the nucleus of an atom a. it is where all of the particle s of the atom are located b. it is the negatively charged part of the atom c. it is where the electrons and the protons are located d. it is the part of the atom with the greatest mass

When the oxygen produced by photosynthetic plants in the water dissolves in the water, which of these is being formed?