题目

---Fang Yong-gang was given ______ honor of being one of the 10 yearly figures in China, 2007.---That's really ________ great encouragement to those serving in the army.A. the; 不填                     B. a; a            C. the; a                D. 不填; the 答案：C灰锡（以粉末状存在）和白锡是锡的两种同素异形体．已知：①Sn（s，白）+2HCl（aq）═SnCl2（aq）+H2（g）△H1②Sn（s，灰）+2HCl（aq）═SnCl2（aq）+H2（g）△H2③Sn（s，灰）   Sn（s，白）△H3=+2.1kJ?mol-1，下列说法正确的是（ ）A．△H1＞△H2B．锡在常温下以灰锡状态存在C．灰锡转为白锡的反应是放热反应D．锡制器皿长期处在低于13.2℃的环境中，会自行毁坏