They change the air from water vapor (gas) to liquid water. This can produce clouds you see in the sky or dew or fogs.
The answer is; the skeletal system and the nervous system
The skeletal system (muscle and bone) give you rigidity and enable your legs to support your weight. The muscles also act on the bone as a fulcrum allowing it possible for them to contract and make motion possible.
The nervous system is important in the coordination of movement. The brain is the center for locomotor action. This ensures you are able to place one foot in front of the other in sequence and moving your arm in concert.
I think it the answer is C ( The relationship between the bacteria and the ticks is commensalism, and the relationship between ticks and humans is parasitism.
-- Alina (:
