Explanation:

- Phytoplankton: These are microscopic marine algae, crucial for aquatic ecosystems as primary producers but not carnivorous plants.

- Bladderwort: This is a carnivorous plant with specialized bladder-like traps that capture and digest tiny aquatic prey.

- Venus flytrap: A perennial carnivorous plant from the sundew family, it uses its jaw-like leaves to trap insects and secretes digestive enzymes.

- Seaweed: A marine algae and not carnivorous. It's a major part of ocean plant life, but it doesn't trap or digest prey.

Correct Answer: Venus flytrap