鹰嘴滑囊炎的常见病因是（）
A.血液透析
B.感染
C.肘部的一次直接打击
D.静脉内给药的误用
E.肘部直接受压的重复小创伤
参考答案：E
证券公司可以间接为客户从事期货交易提供融资或者担保。（）
Which of the following market structure characterized that a large number of competitors produce (slightly) differentiated products with low barriers to entry（）
A. Perfect competition.
B. Monopolistic competition.
C. Oligopoly.
