现有氧化铁、稀硫酸、氢氧化钠溶液、氯化钡溶液和碳酸钾溶液五种物质，在常温下它们两两相互发生的化学反应有[ ]
A.4个
B.5个
C.6个
D.7个
答案：B
— I hear Daming has gone to Hainan Island for his holiday.
— Oh, how nice! Do you know when he ? [ ]
A．was leaving
B．had left
C．has left
D．left
固位形鸠尾峡的宽度前磨牙一般为颊舌尖宽度的（）
A.1/5
B.1/3
C.1/2
D.2/3
E.3/4
