Organic molecules ____.

A) are held together primarily by hydrogen bonds
B) are found only in nonliving organisms
C) were present on Earth before the appearance of cells
D) contain only carbon and hydrogen
E) are found only in living organisms

Organic molecules, which contain carbon and hydrogen, were present on Earth before the appearance of cells. They are also found in living organisms, but not exclusively. The other answer choices are incorrect. Organic molecules are held together by covalent bonds, not hydrogen bonds (A), and can be found in both living and nonliving organisms, not just nonliving organisms (B). Organic molecules can contain other elements besides carbon and hydrogen (D). Finally, organic molecules are not restricted to living organisms only (E).