Question

an organism that lives in or on another organism, often with harmful side effects —but without benefits is a ________.

• bacterium
• virus
• parasite
• pest

Explanation:

To solve this, we analyze each option:

• Bacterium: Some bacteria are beneficial, not all are harmful or parasitic.
• Virus: Viruses invade cells but the definition here is about living in/on another organism with harm and no benefit, which is more specific to parasites.
• Parasite: By definition, a parasite lives in or on another organism (host), harms it, and gets benefits (while the host gets no benefit), matching the description.
• Pest: Pests are generally organisms that damage crops, property, etc., not specifically defined by living on another organism for survival.

Answer:

C. Parasite