Scientists hypothesize that prokaryotes evolved before eukaryotes because
a. ribosomes closely resemble prokaryotic cells.
b. the meteorites that have struck Earth contain fossils only of prokaryotes.
c. the oldest fossilized cells resemble prokaryotes.
d. laboratory experiments have produced ribosomes abiotically.
e. prokaryotic cells lack nuclei.

e. prokaryotic cells lack nuclei.

Explanation: Prokaryotes are unicellular (single-cell) organisms that lack well developed cell internal membrane-bound structures or organelles. They do not have a nucleus but generally, they have a single chromosome that possess a double-stranded DNA located in an area of the cell called the nucleoid. Most prokaryotes have a cell wall outside the plasma membrane.

because of

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.