I will take a stab at it, but there are not equations, did you forget them?
A. <span>the layer of rock and mineral fragments that covers nearly all of Earth's land surface</span>
Explanation:
pH indicators are weak acids that exist as natural dyes and indicate the concentration of H+ (H3O+) ions in a solution via color change. A pH value is determined from the negative logarithm of this concentration and is used to indicate the acidic, basic, or neutral character of the substance you are testing.
