酸雨被称为大面积破坏环境的“空中死神”,究其原因,与下列哪项人类活动无关 [ ]
A.汽车尾气的排放
B.燃煤废气的排放
C.开发沼气新能源
D.垃圾焚烧
答案:C
While I was in the Disneyland, I saw some children _____ in the roller coaster, laughing happily. [ ]
A. sit
B. seat
C. to sit
D. sitting
压力容器主要受压元件发生()等危及安全的现象时应紧急停运。
A、裂缝
B、鼓包、变形
C、泄漏
D、衬里层失效
E、腐蚀