FILL IN THE BLANK: Paleontologists study ancient organisms. Over millions of years, sediment hardens into rock and preserves the remains of living
things. A
is the impression that an organism or part of
an organism leaves in rock.

im not exactly sure but i think its b!

answer:

the answer is 6 valence electrons.

explanation:

valence is the # of electrons on the outer most shell of an atom.

oxygen has 6.

although, the valency of oxygen is 2, because it only needs to make 2 covalent bonds, or gain 2 electrons, to achieve the stable octet configuration of a noble gas.

that's it!

if you need further assistance, let me know: )

~ trueboss72