引起急性胆囊炎最主要的病因是
A．胆囊管狭窄B．胆囊结石堵塞胆囊管C．胰液反流D．胆囊内蛔虫E．致病菌入侵
参考答案：B
翻车变的功率是多少？
A figure eight knot is used to（）.
A.be a stopper
B.shorten a line
C.join lines of equal size
D.keep a line from passing through a sheave
