It is C, the cell membrane. The membrane is responsible for controlling what goes in and out of the cell by using diffusion and osmosis. The cell wall's purpose is to give shape to the cell, so the answer is C.
The cell is a logical entity: it is a compartmentalized compartment by a cell membrane (or cytoplasmic membrane) in which are grouped all the living molecules (organelles and nutrients). Without this membrane these biomolecules would be diluted in the surrounding environment.
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".
