简述全冠的种类。
参考答案：全冠的种类有：①金属全冠，铸造全冠和锤造全冠；②非金属全冠，塑料全冠和烤瓷全冠；③金属与非金属联合全冠。
The last story ______ our teacher told us the other day was ________ of an Italian explorer.
A．that; which
B．which; which
C．that; that
D．which; that
下列物质可以看成为酚类的是 [ ]
A．
B．
C．
D．
