单项选择题
A. show that organic crops are safer than conventional ones B. be specially trained C. improve soil quality D. poison you E. be eaten F. affect their nutritional content
A．is costly to the police. B．could be a social issue. C．is the only way to prove innocence. D．has been a profitable business.
A．They became less aggressive towards other creatures. B．They lost interest in people. C．They started eating more. D．Other animals started working with them.