单项选择题
A device used to enlarge the size of an existing bore hole，having teeth arranged on its outside circumference to cut the formation as it rotates is a（n）（）.
A.Enlarger bit B.Casing bit C.Hole opener D.Casing opener
单项选择题 A “figure eight” knot is used to（）.
单项选择题 “15 02 41 Semi Double Queen 195 332mm”is a description of（）.
单项选择题 （） is true.
