A、It sends out signals for help. B、It takes over the driving immediately. C、It stops the car automatically. D、It sounds an alarm

When a sleepy driver has trouble with keeping his eyes on the road and gets too close to another car, an alarm sound will warn the driver. [20] If nothing is done, the car will automatically come to a stop and in this way prevent an accident. This is a new device which will soon be tested in an experimental car in Japan. [22] The computer warning system keeps track of a driver’s condition by monitoring his heartbeat with signals transmitted from a band around his wrist. The wristband records the driver’s pulse which measures the heartbeat. Each pulse in the wrist sends a signal to the computer. By analyzing the pulse rate, the computer can determine whether a driver is drunk, sleeping or ill. Devices in other parts of the car can also tell the computer if the car is too close to another vehicle or is moving dangerously. [21] The computer will sound the alarm when a problem arises, and will automatically stop the car if the driver ignores the warning.
Questions 20 to 22 are based on the passage you have just heard.
20. Why is a computer system installed in an experimental car?
21. What does the computer system do first when a problem arises?
22. What is special about the new computer system?