A) interspecific competition kept Chthamalus from extending lower into the intertidal area.
B) intraspecific competition kept Chthamalus from extending lower into the intertidal area.
C) a limiting factor kept Chthamalus from extending lower into the intertidal area.
D) a barnacle parasite kept Chthamalus from extending lower into the intertidal area.
E) predation kept Chthamalus from extending lower into the intertidal area.