The vertical zonation of sessile marine species in the intertidal zone is a longexamined phenomenon. This particular tide-cycle study examined the incidence of two sessile animal species, the common mussel (Mytilus edulis), and the acorn barnacle (Semibalanus balanoides), in plots of increasing altitude in the intertidal zone of a beach preserve in coastal Massachusetts. Results showed that incidence of Mytilus increased in frequency as height decreased, and incidence of Semibalanus increased in frequency as height increased, up to the high-tide line or "barnacle line." This distribution suggests competition between the two species, with the mussel successfully out-competing the barnacle for more time underwater and the barnacle evincing more ability than the mussel to reside in less ideal conditions. The transitional conclusion indicates that barnacles display numerous adaptations that equip them for life in the upper tide zone.

If the information provided in the passage is accurate, which of the following must also be true?

(A) Some sessile species do not live in coastal areas.
(B) Semibalanus would prefer by nature to live below the water level than above it.
(C) The main food source of Semibalanus inhabits coastal areas at the level of the high-tide line.
(D) Sessile species thrive in cold Atlantic waters better than in temperate tropical waters.
(E) Semibalanus cannot survive in the upper tide zone.



Which of the following, if true, best strengthens the author's conclusion?

(A) In tropical waters where there are no mussels, barnacles live predominantly close to the high-tide line.
(B) Barnacle concentration decreases as the high-tide mark decreases.
(C) Mussels can survive in air-only environments three times longer than barnacles.
(D) Barnacles are able to feed on land-based flora, while mussels can only gain nutrition from underwater species.
(E) When a larger geographical area is studied, the incidence of mussels matches that of barnacles.