The right answer is A.
The foreshore, also called intertidal zone, is the tidal zone of the tides on the coast. The alternation of the tides which discover more or less the substrate according to the phases of the Moon determines the conditions of humidity, salinity and temperature of the foreshore.
These variations lead to a vertical ecological structuring of the foreshore in so-called supralittoral, mediolittoral and infralittoral stages. The floristic and faunistic stands of these stages are distinct, according to the requirements of organisms in water, salinity and temperature. Therefore it would be beneficial for organisms living in this period that it can live without depending on the water present in their environment since the presence of the latter is inconstant.
The foreshore is divided into several floors that correspond to different ecological conditions. These coastal stages are defined by the duration of their emergence and therefore by the level of the different tides.