That would be the nervous system.
Answer: The nucleus.
Explanation: In an atom, there are two main parts, the nucleus and the electron cloud/electron shells. The protons and neutrons are located in the nucleus, and the electrons are located in the electron shells/cloud/whatever.
C.
The force the wind exerts on the surface of the rock while it blows past it can cause it to erode into irregular shapes.
Osmosis! Osmosis is the process that water diffuses across the plasma membrane.
