Amutagen is

a) a living thing that has undergone a mutation.
b) an agent that causes a mutation in dna.
c) a mutation that has affected one gene.
d) a chemical that can poison living cells.

The correct answer is B) An agent that causes a mutation in the DNA.

Mutagen is a chemical or a physical agent that brings change in the genetic material of an individual and therefore increases the chances of mutation(permanent change in the genetic material).

Therefore, it is an agent that causes mutation in the DNA.

Example of mutagen- Ionizing radiation (like X- rays) , UV radiations.

answer: - few nutrients

high pressure

low temperatures

explanation: 1. few nutrients:   open-ocean zone is located way far from the land, which is the main source of the essential nutrients.2. high pressure: pressure increases by 1 atmosphere for every 10 meters increase in depth.3. ample sunlight: a large fraction of the sunlight is reflected back to the atmosphere from the sea surface. 4. varying salinity: below the thermocline, the water is isolated from the atmosphere so the salinity remains stable over the year.5. low temperatures:   the temperature of open-ocean zone ranges from a low of -2°c to an average of 17°c