In a cactus, carbon is fixed only during the day. this is because cacti need sunlight to perform photosynthesis. Have a great day :)
The outer planets are D. larger and less dense.
The outer planets are known as the gas giants they have no solid surface.
The inner plants are much smaller and do have solid surfaces.
Hope this helps.
All of those systems are vital for a person to survive. If an organ stopped functioning it could cause you to die unless it is your liver and a few others.