Professor James will give up a lecture on the Western culture,but when and where _______ yet.

A．hasn’t been decided

B．haven’t decided

C．isn’t being decided

D．aren’t decided

矿井应当根据矿井的（）、水文地质条件、煤层赋存条件、围岩物理力学性质、开采方法及岩层移动规律等因素确定相应的防隔水煤（岩）柱的尺寸。