Four flasks are prepared with a broth that supports microbial growth. Broth A is boiled and then sealed to prevent the entry of air. Broth B is boiled and left open to the air. Broth C is boiled and left open, but the flask is fitted with an S-shaped neck. Broth D is boiled, left open to the air, and fitted with an S-shaped neck, but after two days the neck is removed. If the broths are examined after four days, which ones will contain living microorganisms?

Question

Quizplus · Accepted Answer

Broth B is left open to the air, which means it will allow the entry of microorganisms and support their growth. Broth D is initially fitted with an S-shaped neck, which would prevent the entry of microorganisms, but once the neck is removed after two days, it becomes exposed to the air and will support the growth of microorganisms. However, Broth A is boiled and then sealed to prevent the entry of air. Therefore, no microorganisms will be able to grow in it. Broth C is boiled and left open, but it has an S-shaped neck, which will prevent the entry of microorganisms into the flask. Therefore, it will not have any living microorganisms after four days. Thus, the correct choice is C – broths B & D.

Four Flasks Are Prepared with a Broth That Supports Microbial