During which stage of sleep does body temperature begin to fall?
a. stage 2 sleep
b. stage 3 sleep
c. stage 4 sleep
d. rem sleep

A.
In stage two our  body temperature begins dropping and heart rate starts slowing down.The website below should help you with any additional information about the stages of sleep. Hope this helps :)
http://psychcentral.com/lib/stages-of-sleep/

a. stage 2 sleep.

Explanation:

Most people don't no that sleep has specific stages, which are:

Stage 1: This is the lightest stage when you can wake up easily. During this stage is present slow eyes movements, muscles start to relax and brain waves start to slow. Due to the light stage of the sleep, people often experience falling sensations.Stage 2: During this stage we don't wake up easily and eyes movement stop, the body temperature begins to fall and heartbeats begins to slow.Stage 3: This stage is characterized for the delta waves emitted by the brain, which are slow brain waves. During this stage can be present sleepwalking, sleep-talking or somniloquy.Stage 4 (REM sleep): This is the dreaming stage, when is present rapid eyes movements. Also, brainwaves are more active than other stages, awakenings can happen easily and give a sense of felling groggy.