第3题: [单项选择]Passage Three Questions 33 to 35 are based on the passage you have just heard. A. To protect beachfront property. B. To reduce the traffic on beach roads. C. To provide privacy for homeowners. D. To define property limits. 参考答案:A 答案解析:[听力原文] 33-35 Your professor has asked me to talk to you today about the topic that should be
第14题: [单项选择]要使自凝树脂在常温下就能聚合,需要有() A. 叔胺等促进剂 B. BPO等引发剂 C. 阻聚剂 D. 紫外线吸收剂 E. 单体 参考答案:A 答案解析:自凝树脂的聚合过程与热固型树脂相似,所不同的是链引发阶段产生自由基的方式不同。BPO需要在60~80℃温度下才能分解出自由基,欲使其在常温下分解出自由基,需要叔胺作为促进剂。BPO与叔胺在常温下就能发