Which statement correctly describes what atoms and molecules are made of?
A. Molecules are made of atoms, and atoms are made of protons,
neutrons, and electrons.
B. Molecules are made of protons and neutrons, and atoms are
made of electrons and protons.
C. Atoms are made of protons and electrons, and molecules are
made of neutrons and electrons.
D. Atoms are made of molecules, and molecules are made of
protons, neutrons, and electrons.

True or false: the cycle of seasons on the earth is caused by the tilt of the earth on its axis toward and away from the sun.

If a spring has a k value of 100 newtons per meter and it is stretched 0.50 meters, what is the restoring force of the spring?

Cells in the nervous system have a potential difference of 70 mv across the cell membrane separating the interior of the cell from the extracellular fluid. this potential difference is maintained by ion pumps that move charged ions across the membrane. is this an emf? select the correct answer and explanation. 1)no. the ion pumps cannot separate charges; thus, they cannot create a potential difference. 2)yes. the ion pumps cannot separate charges, but they still can create a potential difference. 3)yes. the ion pumps can actively separate charge; thus, they can create a potential difference. 4)no. the ion pumps can separate charges, but they cannot create a potential difference.