下列物质中，以极性共价键结合的是[ ]
A．MgO
B．NaCl
C．H2
D．H2O
答案：D
25. Australia is an island continent lying between ____ .
A．the Pacific Ocean and the Atlantic
B．the Indian Ocean and the Atlantic Ocean
C．the Arctic Ocean and the Pacific Ocean
D．the Pacific Ocean and the Indian Ocean
外科疾病辨证的总纲是（）
A.脏腑
B.经络
C.气血
D.阴阳
E.局部
