To be honest, since we live on Earth (assuming you do as well), Earth is the easiest planet to study. We don't know much about the other planets because we've never been to any of them. I believe that the second easiest planet to study is either Uranus or Saturn.
The answer is C. thousands of galaxies
because<span> Hubble found 10,000 of galaxies just by observing one small little area in space.
So, it has to be thousands.</span>
Photosynthesis and cellular respiration both somewhat involve each other.
C hydrosphere, lithosphere, biosphere
Release digestive enzymes and absorb digested organic material.
Really hope this helps
