单选题
The primary topic of the passage is which of the following?
(A) The origin of bioluminescence in plankton, predators
(B) The disadvantages of bioluminescence in microorganisms
(C) The varieties of marine bioluminescent life forms
(D) Symbiotic relationships between predators and their prey
(E) Hypotheses on the causes of bioluminescence in plankton
【正确答案】
E
【答案解析】The author first states that the reasons for bio-luminescence in underwater microorganisms is obscure and then proceeds to enumerate various hypotheses.