Which one of the following groups of animals reproduces only by sexual means?
- Cnidaria
- Porifera
- Protozoa
- Ctenophora
Answer
(4) Ctenophora
Solution
As per NCERT, in ctenophores (comb jellies) reproduction takes place only by sexual means; fertilisation is external with indirect development.
∵ Cnidarians (budding), sponges (fragmentation) and protozoans (fission) also reproduce asexually, options (1), (2) and (3) are ruled out.
Answer: (4)