How do biological systems respond when acids or bases are added? Biological systems do not experience any changes in pH.

Biological systems do not experience any changes in pH.

Cells produce different molecules that can function at the new pH levels.

Cells produce different molecules that can function at the new pH levels.

Most biological molecules can function at any pH value.

Most biological molecules can function at any pH value.

They have substances that counteract acids or bases to prevent the pH from changing.

The correct answer is - They have substances that counteract acids or bases to prevent the pH from changing.

Explanation:

Including human, all the organism depends on the water so therefore known as waster system based which suggests that they depend on the acid-base liquid equilibrium to maintain its cellular functions and homeostasis.

Acid and bases are influences and determine the pH value of the chemistry of biological systems as every cycle is affected by the pH fluctuation so the maintenance of pH is very critical.

so as to keep biological system compound and in the equilibria of protonation, they have certain substances in each cycle or part that counteract the acid and base to maintain pH.  

for instance:

phosphate ion  maintains the Cytoplasm pH

the bicarbonate ion regulates the Blood pH