Which of the following statements CORRECTLY describes the obligate anaerobic bacteria?

Explanation

Obligate anaerobic bacteria are organisms that cannot survive in the presence of oxygen. Oxygen is toxic to them, and they only thrive in environments devoid of it. This distinguishes them from aerobic bacteria, which require oxygen, and facultative anaerobes, which can survive with or without oxygen. Understanding these distinctions helps clarify that the correct statement about obligate anaerobes is that they are killed by free oxygen, as described in Option A. Options B, C, and D incorrectly describe characteristics of other types of bacteria or misrepresent the nature of obligate anaerobes.