【单选题】This is so difficult a question _____.
A.
that many students can't answer
B.
which many students can’t answer it
C.
as no one can answer it
【简答题】This article is so difficult that it is _________ our understanding.
【判断题】在使用仪器前,要进行检查,而且为了不干扰调查对象,保持观察场景的自然状态,严禁公开使用观察仪器。( )
【简答题】什么是绝对高程 ? 什么是相对高程 ? 绝对高程又被称为什么?