控制测量
参考答案：
在一定区域内，为地形测图和工程测量建立控制网所进行的测量。
在冰雪道路上行车时，车辆的稳定性降低，加速过急时车轮极易空转或溜滑。
He made another wonderful discovery, _______ of great importance to science.
A．which I think is
B．which I think it
C．which I think it is
D．I think which is
