Explanation:

- Option 1: Fission: This typically occurs in simple, unicellular organisms where the cell splits into two or more cells. Red algae, being complex multicellular organisms, do not reproduce through fission.

- Option 2: Spore formation: This is a form of asexual reproduction involving spores, but it's not a vegetative method and not typical for red algae's vegetative reproduction.

- Option 3: Cutting: Generally applies to plant propagation in higher plants using portions of the plant body, not typical for red algae's vegetative reproduction.

- Option 4: Fragmentation: Algae pieces break off and grow into new individuals. This is a form of vegetative reproduction commonly observed in red algae.