25. ________ theme of the Shanghai Expo is “Better city, better life”.  It will send _____ message to people around the world to care about the places where they live.

A．/…a

B．the…a

C．a…the

D．/…the

氧化锌丁香油水门汀的性能特点是：

A．是热和电的绝缘体，对牙髓无害

B．溶于唾液

C．弹性模量和银汞合金相似

D．足以承受银汞合金压力