髌骨横骨折，造成的原因可能是（）。
A.韧带损伤
B.肌肉拉力
C.积累劳损
D.直接暴力
E.骨骼疾病
参考答案：B
解析：肌肉牵拉暴力常致髌骨横形骨折。
Theophylline ethylenediamide is administered to a client with COPD. The nurse knows that the medication is for which of the following purpose（）
A. To reduce bronchial secretions.
B. To relax bronchial smooth muscle.
C. To strengthen myocardial contractions.
D. To decrease alveolar elasticity.
离心式通风机和轴流式通风机一般采用什么方法反风？
