Biology

The correct answer is: A.A flea.

A flea is an example of a parasite because it lives off its host (typically a mammal like a dog, cat, or human) and benefits by feeding on the host's blood, often harming the host in the process. Fleas can cause discomfort, skin irritation, and in some cases, transmit diseases.

Why the other options don't apply:

B.An orchid: Orchids are plants, and many orchids are epiphytes, meaning they live on other plants, but they don’t harm their host. In some cases, orchids can be commensal (not benefiting or harming the host), but they are not parasites. Orchids do not typically extract nutrients from their host plants, so they don't fit the definition of a parasite...