Answer:
Universe.
Explanation:
Biosphere is just a planet. Solar system contains planets and star. Galaxy holds multiple solar systems only. Universe hold everything, biospheres, solar systems, and galaxies. I hope this helps :D
B because....................
A covalent compound is made when two or more nonmetal atoms bond by sharing valence electrons. The shared valence electrons between two nonmetal atoms is called a covalent bond. Covalent bonds are formed when two atoms begin sharing electrons.
I believe the answer is: Protons and Neutrons
Protons weigh 1 amu while neutrons also weigh 1 amu. I’m not sure if they are talking about how many there is.