第14题: [单项选择]大多数堤防都修筑成()的堤顶。 A. 水平 B. 中间低 C. 中间高、向两侧倾斜 D. 不断变化 参考答案:C
第15题:[单选题]The Ground Proximity Warning System (GPWS) generates aural and visual warnings, its working range is: A. A. Below radio altitudes 2 450ft. B. B. Between radio altitudes 30ft and 1 500ft. C. C. Between radio altitudes 30ft and 2 450ft. 参考答案:C