多项选择题

DirectiOns: For the following questions, select the two answer choices that, when used to complete the sentence, fit the meaning of the sentence as a whole and produce completed sentences that are alike in meaning. Studded starfish are well protected from most predators and parasites by ______ surface whose studs are actually modified spines.

A. a vulnerable
B. an armored
C. an obtuse
D. a brittle
E. a concave
F. a rugged