Final answer:
Polychaetes differ from other annelids primarily due to the presence of parapodia, which are paired appendages bearing numerous bristles and are used for movement and respiration. The correct answer to the question is option (b) Have parapodia.
Step-by-step explanation:
Polychaetes are distinguished from other annelids in several ways, but one of the most notable features of polychaetes is their parapodia. These are fleshy, paired appendages that protrude from each body segment and bear numerous bristles, also known as chaetae. The parapodia serve several functions including locomotion and respiration.
In contrast, oligochaetes such as earthworms lack these parapodia and typically have fewer bristles or none. Polychaetes are part of the phylum Annelida and are mostly marine worms that can be found in various environments including hydrothermal vents where some species engage in symbiotic relationships with bacteria.
In the context of the question, the presence of parapodia is what sets apart polychaetes from other annelids. Therefore, the correct option is (b) Have parapodia.