Option 1

Option 1. It prevents changes in the pH of the growth medium, ensuring that the culture medium remains stable.

Sam: I do remember that maintaining the right pH is important in cellular function; it helps maintain the correct protein structure and thus preserves cellular function. I don’t think this is relevant to aseptic technique, though. 

Dr. Spencer: That’s right, Sam. How about you give this another try?

Option 2. It minimizes the risk of contamination, allowing for accurate and reliable results by preventing growth from unwanted microorganisms.

Option 3. It prevents the contamination of the sample with other microorganisms, which could inhibit the growth of the causative agent.