Given the task definition and input, reply with output. In this task, you are given a context, a subject, a relation, and many options. Based on the context, from the options select the object entity that has the given relation with the subject. Answer with text (not indexes).

Context: Intertidal ecology is the study of intertidal ecosystems, where organisms live between the low and high tide lines. At low tide, the intertidal is exposed whereas at high tide, the intertidal is underwater. Intertidal ecologists therefore study the interactions between intertidal organisms and their environment, as well as between different species of intertidal organisms within a particular intertidal community. The most important environmental and species interactions may vary based on the type of intertidal community being studied, the broadest of classifications being based on substrates - rocky shore and soft bottom communities., A rocky shore is an intertidal area of seacoasts where solid rock predominates. Rocky shores are biologically rich environments, and are a useful "natural laboratory" for studying intertidal ecology and other biological processes. Due to their high accessibility, they have been well studied for a long time and their species are well known., Chalk is a soft, white, porous, sedimentary carbonate rock, a form of limestone composed of the mineral calcite. Calcite is an ionic salt called calcium carbonate or CaCO. It forms under reasonably deep marine conditions from the gradual accumulation of minute calcite shells (coccoliths) shed from micro-organisms called coccolithophores. Flint (a type of chert unique to chalk) is very common as bands parallel to the bedding or as nodules embedded in chalk. It is probably derived from sponge spicules or other siliceous organisms as water is expelled upwards during compaction. Flint is often deposited around larger fossils such as Echinoidea which may be silicified (i.e. replaced molecule by molecule by flint)., Calcareous is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines., Corallina officinalis is a calcareous red seaweed which grows in the lower and mid-littoral zones on rocky shores . It is primarily found growing around the rims of tide pools , but can be found in shallow crevices anywhere on the rocky shore that are regularly refreshed with sea water . It predominantly grows on the lower shore , especially where fucoid algae are absent , but is also found further up shore on exposed coasts . It forms calcium carbonate deposits within its cells which serve to strengthen the thallus . These white deposits cause the seaweed to appear pink in colour , with white patches where the calcium carbonate is particularly concentrated , such as at the growing tips . The calcium carbonate makes it unpalatable to most rocky shore grazers ., Subject: corallina officinalis, Relation: taxon_rank, Options: (A) form (B) species (C) variety
species