【简答题】经纬仪光学对中的步骤( )。A. 将三脚架安置在测站点上,目估使架头大致水平并使架头中心粗略对准测站点标志中心; B. 调节光学对点器目镜、物镜调焦螺旋,使对点器十丝影像和测站点标志的影像清晰; C. 移动三脚架腿,观察圆水准器泡,在气泡尽量居中前提下,确保使光学对点器对中; D. 调节三角架的架腿高度,使管水准气泡居中。此时仪器既对中又粗平。
【简答题】阅读理解。 A meteorite(陨石) almost hit an 80-year-old man named Arthur Pettifer in Britain when he was working in his garden. The meteorite was the biggest in the past 26 years in Britain. The meteorite wei...