Some protozoans have special organelles called contractile vacuoles that continually eliminate excess water from the cell. The presence of these organelles, and the constant influx of water from the outside environment tells you that the environment

is hypotonic to the protozoans

Explanation:

The constant influx of water from the outside environment of the cell tells that the environment is hypotonic to the cell.

A hypotonic environment is one with a lower solute concentration than the cytosol. Hence, water osmotically moves from the environment into the cells of the protozoans. The water needs to constantly be removed from the cells, otherwise, they will become turgid and lyse away their contents.

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.

i think the answer would be d