反丝钻杆的作用是()。A、正常钻进B、处理孔内事故C、增加压力D、防止孔壁坍塌 发布时间:2020-12-08 09:59 │ 来源:www.tikuol.com 题型:单项选择题 问题: 反丝钻杆的作用是()。A、正常钻进B、处理孔内事故C、增加压力D、防止孔壁坍塌
题型:单项选择题 —I'm sorry. I'm late for the music presentation. —Why are you so late? The presentation _______ for 10 minutes. [ ]A. has begun B. has stopped C. has been over D. has finished 查看答案