I think it is C, though not sure. Hope this helps you.
The generally accepted parts of modern cell theory include: All known living things are made up of one or more cells. All living cells arise from pre-existing cells by division. The cell is the fundamental unit of structure and function in all living organisms
The correct answer is that ferns have two part in their life cycle: Diploid phase and haploid phase
The life cycle of a fern has two parts: sporophyte stage and gametophyte stage. The gametophyte stage of ferns are haploid which releases gametes and the sporophyte stage are diploid that produces spores. This kind of life cycle is known as the "alternation of generation".