Lampreys are known to attach themselves to fish. in doing so they rasp off a section of the fish with hard keratinized structures and "feed" on the blood and fluid that oozes into their oral cavity. fish can survive with a lamprey attached, but they have to expend extra energy swimming with the lamprey attached. this association would be designated a:
a) mutualism.
b) parasitism.
c) predation.
d) commensalism.

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.

condenser is used to focus in the light microscope.