[单项选择]{{I}}Questions 14 to 17 are based on the following passage. At the end of the passage, you will be given 20 seconds to answer the questions. Now listen to the passage.{{/I}}Whet does the professor mainly discuss A. How grasshoppers find food. B. How grasshoppers fight other insects. C. How grasshoppers communicate with each other. D. How grasshoppers escape from danger.