To neutralize a base, a(n) must be added. a. acid b. buffer c. weak base d. hydroxide ion

a. acid

Explanation:

The neutralization of a base requires the addition of acid.Hydroxide ions of the base are neutralized using hydrogen ions of an acid.Acid-base neutralization results in the formation of water and salt.

For example: NaOH is neutralized by HCl as:

NaOH + HCl → NaCl + H₂O.

Organisms are more likely to be more preserved in mud than sand because mud is moist and wet, while sand is very dry.