Questions 16 to 18 are based on the passage you have just heard.

Directions:In this section, you will hear three passages. At the end of each passage, you will hear three or four questions. Both the passage and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A, B, C and D). Then mark the corresponding letter on Answer Sheet 1 with a single line through the centre.
  • A They help farmers keep diseases in check.
  • B Many species remain unknown to scientists.
  • C Only a few species cause trouble to humans.
  • D They live in incredibly well-organized colonies.
  • A They are larger than many other species.
  • B They can cause damage to people's homes.
  • C They can survive a long time without water.
  • D They like to form colonies in electrical units.
  • A Deny them access to any food.
  • B Keep doors and windows shut.
  • C Destroy their colonies close by.
  • D Refrain from eating sugary food.