Which of the following could be used to make the simplest circuit?
a. a battery and a wire
b. a battery, wire, and a switch
c. a battery, wire, and a light bulb
d. a battery, wire, switch, and a light bulb

The following that could be used to make the simplest circuit are a battery, wire, switch, and a light bulb. The answer is letter D. The battery provides the energy for the bulb to work. The wire provides a pathway for the electrons to move. The switch provides the open and close of the circuit.

d. air pressure decreases as altitude increases.