单项选择题
他们工作四小时，休息八小时。（）
A. They work four hours and have four hours for rest. B. They work eight hours and have four hours for rest. C. They work four hours and have eight hours for rest. D. They work eight hours and have eight hours for rest.
单项选择题 驾驶台始终有驾驶员值班。（）
单项选择题 后退一！（）
单项选择题 后退二！（）
