The correct answer is option 3: Sorus. A sorus is a cluster of sporangia, which are structures that produce and contain spores. In the case of ferns, the sorus is typically found on the underside of a frond, which is a leaf-like structure. The sporangia within the sorus are responsible for the production and release of spores, which are reproductive cells. The spores are important for the fern`s ability to reproduce and disperse. Options 1 and 2, ramentum and indusium, are not directly related to sporangia-bearing leaves of a fern. Ramentum refers to small, scale-like structures found on various parts of a fern, while an indusium is a protective covering that may be present over a sorus in some fern species. Option 4, sporophyll, refers to any leaf or leaf-like structure that bears sporangia.