Certain corals have been found in extremely deep water. these coral lack the zooxanthellae that are found in tropical coral reefs because zooxanthellae require sunlight to go through photosynthesis and there is no sunlight available at these depths. these deepwater coral often are built upwards instead of across the bottom. why do the polyps build the coral this way?
a.)the pressure of the deep water is too great to build outwards.
b.)they grow to avoid predators.
c.)they are filter feeders.
d.)the temperature of the water keeps them from building outwards.

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.