活塞式压力计用来校验标准压力表时，活塞在受力平衡状态下，应使活塞（）活塞（）为宜。
参考答案：升起；总长的1/3
More wild tigers have been seen in the forest around this area, ____ there used to be very few.[ ]
A. when
B. where
C. what
D. which
运用供求理论试述石油输出国要限制石油产量。
