The nurse is caring for a client admitted to the hospital with a bowel obstruction. The nurse should wear sterile gloves when

A. inserting an indwelling urinary catheter.
B. giving a back rub on intact skin.
C. changing an oxygen system.
D. inserting an IV catheter.

如弯制图所示的蛇形盘管，其有效圈数为28圈，盘管中径为250毫米，节距为30毫米，求蛇形盘管的长度应是多少？