现场施工时绞车为什么必须摆放在正对井口的上风口或侧上风口位置？
参考答案：
防止井口溢出的有害气体可能会造成人员中毒、伤亡。
—Did you go to the cinema to see 3D Titannic last night?
—No, I ________ go to the cinema . The tickets are too expensive[ ]
A. hardly
B. nearly
C. still
D. only
—Did you find the missing couple in the mountain yesterday?
—No, but we ______ to get in touch with them ever since.
A．had tried
B．have tried
C．have been trying
D．had been trying
