Asolution is a a. combination of isotopes. b. chemical reaction. c. mixture in which

(C) because when substances dissolve in it completely, it is called solution which has a even colour all over and no things settled down. But when we see undissolved things that do not settle down, it is called an colloid which make the visibility through it a little opaque and not clear like in the solution

Robert Hazen’s studied enviromental and biological processes that might have been critical for life, and also for the formation of approximately two-thirds of Earth's mineral species (see Hazen et al., 2008; Gonzalez & Richards 2020) .

Explanation:

Hazen provided evidence about how first organic molecules were generated on the primitive earth millions of years ago. He observed that high-pressure hydrothermal vents may provide food for underwater ecosystems. It represents a piece of critical evidence on the origin of life.

You can read these articles that are certainly clarifying in the description of his experiments and discoveries:

1- Hazen, R. M., Papineau, D., Bleeker, W., Downs, R. T., Ferry, J. M., McCoy, T. J., ... & Yang, H. (2008). Mineral evolution. American Mineralogist, 93(11-12), 1693-1720.

2- Gonzalez, G., & Richards, J. W. (2020). The privileged planet: how our place in the cosmos is designed for discovery. Gateway Editions.