下列关于骨牵引的注意事项描述正确的是
A、注意牵引两侧有无阻挡，以免减低牵引力
B、注意针眼护理，防止感染
C、注意牵引针有无滑动或将皮肤拉豁
D、防止压迫性溃疡
E、卧床休息，禁止活动肢体，防止意外发生

An organisation has the following total costs at two ac...

单项选择题An organisation has the following total costs at two activity levels:
    Activity level (units)        17,000         22,000
    Total costs (5,000 in the total fixed costs when activity exceeds 18,000 units.
What is the total cost at an activity level of 20,000 units?

一件好的高级珠宝，一定是设计，工艺，（ ）这三者的结合。（ ）A．品牌 B．材质

单项选择题一件好的高级珠宝，一定是设计，工艺，（ ）这三者的结合。（ ）

_____  is a hormone secreted by the thymus that can sti...

单项选择题_____  is a hormone secreted by the thymus that can stimulate the immunological activity of lymphoid tissue.