In this section, you will hear several passages. Listen to the passages carefully and then answer the questions that follow. Questions 11 to 14 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. What is the source of the ethylene described in the talk
A．The fruit itself. B．The air surrounding the fruit. C．The spray applied by farmers. D．The tree or vines to which the fruit is attache