阅读理解：
Denny
Denny can detect, within a 150-foot radius, the presence of anything or anybody that shouldnt be there. Its swiveling head contains microwave and infrared sensors that can detect people as well as smoke. In future editions the head will also contain sensors that can smell the weak smell of a human body.
Normal speed of the robot guards is about one mile an hour, and they can even talk: you have been detected, warns the voice from the clever guard. Denny is designed to patrol corridors and other areas after lock-down hours , not to move among people. If, say, a prisoner does get near the corridor where he should not be, itll immediately tell its base station by radio.
31 Denny is a robot guard, who
B has microwave and infrared sensors.
D depends on his built-in radio for distinguishing a friend from an enemy.
A The TV camera.
C The infrared sensor,
33 Which of the following statements is true?
B Denny is able to replace human security guards where people move about freely.
D Denny cannot open doors or watch stairs.
A He cannot tell an enemy from a friend.
C He does not know how to use a weapon.
35 After reading this passages you probably have got the impression that
B Denny moves both in corridors and up and down stairs.
D Denny moves quite slowly.