During the stage of internal combustion engine operation in which the piston rises and compresses the fuel in the combustion chamber,
a. both the intake and exhaust valves are closed.
b. both the intake and exhaust valves are open.
c. the exhaust valve is open and the intake valve is closed.
d. the intake valve is open and the exhaust valve is closed.

Sally turns on her cellular telephone to speak to her friend who is located thousands of miles away. which of the following best describes how such a telephone is able to transmit and receive information? a. the cellular telephone transmits, receives, and encodes information using only sound waves. b. the cellular telephone transmits, receives, and encodes information using only electromagnetic waves. c. the cellular telephone transmits information by electromagnetic waves to a receiver which then encodes them and produces sound. d. the cellular telephone transmits information by sound waves to a receiver which then encodes them and produces electromagnetic waves.