On the wall hung an overcoat, _______color is blue.
whose B. of which C. which D. its
答案:A
老年人对黄,蓝色的辨认率最困难。
在石门向煤层至少打( )个测压孔,测定煤层瓦斯压力,并在打钻过程中采样,测定煤的坚固性系数和瓦斯放散初速度,按综合指标进行预测。
A.2
B.3
C.4
D.5