1. The author refers to the ocean bottom as a "frontier" in line 2 because it (A) is not a popular area for scientific research (B) contains a wide variety of life forms (C) attracts courageous explorers (D) is an unknown territory
1. The author refers to the ocean bottom as a"frontier" in line 2 because it(A) is not a popular area for scientific research(B) contains a wide variety of life forms(C) attracts courageous explorers(D) is an unknown territory