Answer:
fluorine plus chlorides think
The solution is buffered with a weak acid and it's conjugate base. Since NaOH is a base, you can use a weak acid as it's buffer.
The answer to this is Nervous system.
Anything that has mass and occupies space.
Because the 4s orbital is at a lower energy level.
The 4s orbital has a lower energy because it is more <em>penetrating</em> than a 3d orbital. A 4s electron can get closer the nucleus than a 3d electron, so it has a lower potential energy.
The other options are incorrect because they contradict the correct one.