【简答题】You are going to hear a passage about High-speed rail (HSR) in China. Listen carefully and fill in the missing information.
【简答题】源头产生的 NO 排放到大气中之后,最终都会被氧化成 。
【判断题】在某点上,大地水准面超出椭球面的高差是大地水准面差距。
【单选题】After this accident we are ______ concerned with the safety of travelling by high-speed rail. [ ]