Which statement is true about obligate anaerobes?

• A. They require oxygen for growth.
• B. They cannot survive in the presence of oxygen.
• C. They can grow equally well with or without oxygen.
• D. They use oxygen as their final electron acceptor.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the definition of obligate anaerobes. These are microorganisms that cannot survive in the presence of oxygen because oxygen is toxic to them.
2. Step 2: Recall that obligate anaerobes do not use oxygen for their metabolic processes; instead, they rely on other molecules as their final electron acceptors during cellular respiration or fermentation.
3. Step 3: Compare the given statements with the characteristics of obligate anaerobes: they do not require oxygen, cannot survive with oxygen, do not grow equally well with or without oxygen, and do not use oxygen as the final electron acceptor.
4. Step 4: Identify the statement that matches the known biology of obligate anaerobes: 'They cannot survive in the presence of oxygen.'
5. Step 5: Conclude that this statement is true because obligate anaerobes are harmed or killed by oxygen, which distinguishes them from facultative anaerobes or aerobes.