China’s box office income increased to $1.5 billion in 2010, film-makers need to make even better movies to compete with Hollywood. A. as B. or C. so D. but 答案:D新型材料的研制与应用推动了现代高新技术的发展.氮化硅(Si3N4)是一种高温陶瓷材料,它的硬度大、熔点高、化学性质稳定.工业上制得氮化硅的化学反应方程式为aSi+bN21900 °C.Si3N4;则a、b的数值分别为a=______、b=______.