按启动按钮启动往复泵，调节（）油位，排除膜腔内气体。
A、储药
B、润滑
C、变速箱
D、补偿缸
参考答案：D
— What do you think made Mary so upset?
— ____ her new bike. [ ]
A. Lost
B. As she lost
C. Losing
D. Because of losing
二次函数y=ax2+c（c不为零），当x取x1，x2（x1≠x2）时，函数值相等，则x1与x2的关系是______．
