Which of the following plant reproduces by forming spores?

Rhizopus is a fungus which reproduces by spore formation. The fungal hyphae give rise to a globular structure known as sporangium and his sporangium gives rise to several spores by repetitive division of its nucleus, then each nucleus gets surrounded by a part of cytoplasm and develops into a spore.

Spirogyra reproduces asexually by fragmentation.

Sweet potato reproduces from seed, from the actual storage roots, or from the plant vines.

grapes reproduce asexually by cutting and grafting.