Question

BLACK DOT LIKE STRUCTURE UNDERSIDE OF FERN LEAFLETS ARE = 1.)SPORES 2.)SORI 3.)SPOROPHYLLUS 4.)SEEDS

Answer 1

The black dot like structures are known as sori(which is plural for sorus). The sorus forms a cluster of sporangia on the underside of the fern leaflet seen as the black dots. 

Sporangia are structures in most fungi and other plants that act as the site for the formation and storage of spores. In some fern species, the sorus are surrounded by a tissue known as the indusium which forms a scale of protective layer around the sporangia. 

In ferns these sori are yellowish or dark brown in color and mostly found on the underside or on the edges of a fern leaflet.