Why does nuclear fusion occur in stars but not on Earth? A.
There are no elements on Earth that can undergo fusion.
B.
Too many free neutrons are present on Earth.
C.
Fusion reactions require a lot of heat and pressure.
D.
Elements capable of undergoing fusion can’t be enriched on Earth.

C. Fusion reactions require a lot of heat and pressure

Explanation:

A Nuclear fusion doesn't occur naturally on Earth because it requires temperatures far higher than Earth temperatures. Nuclear fusion takes place only at extremely high temperatures. That's because a great deal of energy is needed to overcome the force of repulsion between the positively charged nuclei.

a  solution  is always transparent, light passes through with no scattering from solute particles which are molecule in size. the  solution  is homogeneous and does not settle out. a colloid is intermediate between asolution  and a  suspension. while asuspension  will separate out a colloid will not.