三线股
参考答案：
指价格低廉的股票。这些公司大多业绩不好，前景不妙，有的甚至已经到了亏损的境地。
____ his homework, the boy went out to play games with his friends.
A．Finished
B．Having finished
C．Being finished
D．To finish
骨关节炎发生发展的最危险因素是（）。
A.重要关节创伤
B.持续的应力或关节负重
C.遗传倾向和骨密度升高
D.年龄
E.吸烟
