Directions:In this section, you will heat" 3 short passages. At the end of each passage, you will hear some 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 2 with a single line through the centre.
A.Catching runaway criminals. B.Scratching the hidden bombs. C.Patrolling the dangerous town. D.Drug-sniffing or bomb-sniffing.