What statement best describes the molecules found in living systems?
a. they contain mostly sulfur, gold, and lead.
b. they are very simple molecules made of carbon and hydrogen
c. they are very complex molecules made mostly of carbon, hydrogen, and oxygen

c

explanation:

molecules found in living systems are very complex molecules made mostly of carbon, hydrogen, and oxygen.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).