Sleep could be best described as a
a. car with the engine started, but parked and idling
b. truck driving on the freeway in the right lane
c. train with cargo being loaded at the start of a trip
d. bicycle riding uphill in the wind

Sleep could be best described as a car with the engine started, but parked and idling. Correct A

Sleep is a biological function.The sleep cycle has five stages: stages 1-4 and the REM (rapid eye motion) sleep stage. Stages 1-4 are also known as NREM or non-REM sleep.