Q.The mode of reproduction in bacteria is by

Bacteria undergo a form of sexual reproduction called conjugation, transferring DNA directly from a donor cell to a recipient cell through a specialised pilus.

Bacteria mostly multiply by asexual binary fission, but they also have parasexual/sexual mechanisms of genetic exchange, of which conjugation is the classic example. In conjugation, a donor ('male', F+) bacterial cell, carrying a fertility (F) plasmid, forms a conjugation tube/pilus that connects it to a recipient ('female', F-) cell, and a copy of plasmid DNA (or occasionally chromosomal DNA) is transferred through this tube into the recipient. This transfer of genetic material between two cells is analogous in outcome (though not mechanism) to sexual reproduction in eukaryotes, since it recombines genetic material from two different bacterial cells. Formation of gametes, zoospore formation and endospore formation are not mechanisms of sexual reproduction in bacteria: bacteria do not form true gametes, zoospores are motile asexual spores seen in some algae/fungi, and endospores are dormant, stress-resistant structures formed by some bacteria for survival, not reproduction.

Conjugation — direct transfer of genetic material between two bacterial cells via a pilus — is the mode of genetic recombination ('sexual reproduction') in bacteria.

Bacteria are prokaryotes and reproduce asexually mainly by binary fission, but they can also exchange genetic material through parasexual/recombination mechanisms, the most well-known being conjugation: a donor ('male', F+) bacterial cell forms a sex pilus that connects to a recipient ('female', F-) cell, through which plasmid DNA (or occasionally chromosomal DNA) is transferred, introducing new genetic variation. Option (b) Formation of gametes describes true sexual reproduction in eukaryotes, which bacteria, lacking a nucleus and meiosis, do not undergo. Option (c) Zoospore formation is a form of asexual reproduction (motile spore formation) seen in certain algae and fungi, not bacteria. Option (d) Endospore formation is a bacterial survival strategy under adverse conditions (e.g., in Bacillus and Clostridium), not a reproductive or recombination process.