Use reasoning to answer the following question.
What is secreted by organisms like frogspawn to become a reef?\nOptions:\n- (A) exocrine glands\n- (B) food and shelter\n- (C) exoskeleton\n- (D) bones\n- (E) Energy\n- (F) Chemical energy\n- (G) plasma\n- (H) Energy.

(C)
Many corals secrete an exoskeleton that builds up to become a coral reef.

Good examples are Bubble coral, Elegance coral, Frogspawn and other Euphyllia corals.

Organisms like frogspawns secrete an exoskeleton that builds up to become a reef.

.

Thus, the answer is (C)