单项选择题
Questions 6-9
Choose FOUR letters, A-G.
Write the correct letters in boxes 6-9 on your answer sheet.
Which FOUR uses are listed for bioluminescence in nature
A．ways of attracting food
B．tracing the spread of diseases
C．mating signals
D．growing trees for street lighting
E．drug trials
F．defensive tactics
G．a torch to identify food