What do viruses and bacteria have in common?

• A. They are microscopic organisms that can cause disease
• B. They are visible to the naked eye
• C. They require sunlight to reproduce
• D. They are both plants

Answer: (C)

Both viruses and bacteria are microscopic agents that can cause disease. They’re too small to be seen with the naked eye, which is why they require a microscope or lab tests to be detected. They don’t rely on sunlight to reproduce—viruses must hijack a host cell’s machinery to replicate, while bacteria typically reproduce on their own through cell division (sunlight isn’t a basic requirement for their reproduction). They aren’t plants. So the shared concept here is that they’re microscopic entities capable of causing illness, not visible without magnification and not dependent on sunlight for reproduction.