Research programs on flight-crew distractions have identified 34 different types of activities that have led to errors in the cockpit. Ninety percent of these fall into one of three broad categories: communication, head-down work, and responding to abnormal situations. A well-known example is the December 1972 crash of an Eastern Airlines on approach into Miami International Airport. The crew was so busy looking at a landing gear light and did not notice that someone had turned off the autopilot by mistake. A review was made of reports of accidents caused by crew error. Nearly half involved a loss of attention because of interruptions, distractions or thinking about one task and forgetting others. Several ideas help crews to prevent errors. Conversation is a powerful distracter so it must be kept brief at critical moments. Head-down tasks greatly reduce the ability to monitor what the other pilot and the aircraft are doing, so one pilot must be clearly assigned to flying pilot-flying (PF) and one to non flying responsibilities pilot-not-flying (PNF). Vital tasks need to be scheduled so that they will not conflict with another vital task. When two important tasks must be performed at the same time, the pilots must set up a scan and avoid letting attention linger too long on either duty. They must treat interruptions as red flags. Research into the way the brain works shows that people can only perform two tasks at the same time in a few circumstances, even if they are skillful in performing each task separately. Broadly speaking, humans have two mental systems with which they perform tasks, they wrote. One involves conscious control; the other is an automatic system that operates largely outside of conscious control. Conscious control is required when the task is new, difficult or dangerous; when an automatic process must be put aside to prevent habit capture going back to an old habit because a new system must be followed.2. The Miami accident in December 1972 was caused by （ ）.