Answer:
presence of setae and parapodia
Explanation:
Annelids are groups of organisms under the phylum "Annelida". They are organisms that possess the following characteristics or features: setae, parapodia, coelom, tentacles etc. However, via the possession of not of the setae and parapodia, annelids have been classified into four major classes viz: Polychaeta, Oligochaeta, Hiradinea and Archiannelida, on the basis of their setae and parapodia mainly.
- Polychaeta: possess numerous setae and parapodia
- Oligochaeta: few setae, no parapodia
- Hiradinea: No setae, no parapodia
- Archiannelida: No setae, no parapodia
Hence, the presence of setae and parapodia will enable the scientists classify annelids into their respective classes.
