At ph= 8, which species is most likely to predominate in solution? pka (-nh3+) = 9.9, pka (-cooh) = 2.3

The NH3 + with a PKa = 9.9

Explanation:

The Pka is a mathematical expression to express the dissociation grade of a substance in a solution, that means with a substance with a pKa small is a strong acid, and in this case since the solution pH is 8, that mean that the substance with high pKa ( lower acid strength)  will predominate in a pH of 8.

altitude, density, pressure

air gets less dense the higher the altitude and also the air pressure is less as altitude rises.

c is the answer because when something is left after something evaporates that shows the chemical change.