The circulatory system because it carries out cellular respiration and transports nutrients around the body
It will be very messy and smelly unless u clean it daily and I do recommend not putting the cats food near the litter box bc the fumes of their feces can cause health related issues.
The large the amplitude the large the rate of energy transfer
the enzyme in your saliva is called amylase. its job is to break down complex starch into a much more simple sugar meaning breaking the polysaccharides into monosaccharides.
I say B. Building Pedestrian friendly walkways, so everyone can do it.