锁住井口连接器使用钻柱补偿器，在坐BOP前的大钩负荷基础上过提约（）千磅、确认连接器锁好。
参考答案：50
We on it for several hours but we haven't yet reached any conclusion.
A．are working
B．work
C．have been worked
D．have been working
边长为a厘米的正方形的边长减少3厘米，其面积减少______．
