The organism pictured belongs to the class chondrichthyes or the fishes.

The correct answer for the blank is-

Cartilaginous fishes.

Chondrichthyes is a class of cartilagenous fishes. This means that they have their entire skeleton system made up of cartilages ( unlike bony fishes whose skeleton is made up of bones) as they are devoid of true bones.

This class of fishes have exposed gills that is there is no preotection of gill slits ( unlike bony fishes, which have protective membrane over gill slits). They bear toothlike placoid scales.

when atoms of different types of elements join together, they make molecules called compounds. water consists of compound molecules made up of 2 hydrogen atoms and 1 oxygen atom. this is why it's called h2o. water will always have 2 times the number of hydrogen atoms as oxygen atoms.

b. read the phase at the intersection of any given temperature and pressure.