Where and in what form does carbon used in cellular respiration come from?

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

Read each description below and determine to which stage of sleep each pertains. then click and drag each box into the appropriate category below.

If your client can successfully complete two or more repetitions above the desired repetition range in the last set in two consecutive workouts for any given exercise, the load should be depending on your client's current physical abilities. increased by 1-5% increased by 2-10% increased by 5-15% increased by 10-20% none of these