The correct answer is option (a) Scanning tunneling microscope.
Microscopes are used to see the objects at molecular level. Scanning tunneling microscope( STM) is a type of optical microscope that uses optics(light) and lenses to see the enlarged size of the object. This microscope use a small metal tip under a high voltage. when this tip of microscope is brought close to the metal, the metallic tip of microscope draws electrons from the atom (metal) to be observed. This generates an electric current. There is a computer system attached to the microscope that detects the change in the electric current. Computer plots the change in position of atoms in metal.
The brain stem controls basic body functions such as breathing, swallowing, heart rate, blood pressure, consciousness, and whether one is awake or sleepy.
