题目

完形填空  阅读短文，从每题所给选项中选出可以入空白处的最佳选项。     Last week Lu visited England. He stayed with my grandmother. He said it was a strange visit. “I don’t understand, but I  1 your grandmother a lot. When I arrived, I gave her a   2  from Suzhou. She looked in it and asked me to take it back. Then I saw a red spider(蜘蛛) on the table so I killed it for her and she seemed very   3 . Do English people like spiders?”     “Later we went shopping. Someone was painting a shop   4  , so there was a ladder. Grandmother  三鹿奶粉加入三聚氰胺后使奶粉的含氮量增大，以此冒充蛋白质．三聚氰胺为白色晶体，无味，密度1.57g/cm3．低毒，常温稳定，高温可分解．牛奶呈中性或微酸性，而三聚氰胺的水溶液呈碱性．目前．我国生产三聚氰胺多采用尿素为原料．反应如下：6CO（NH2）21分子三聚氰胺+6NH3↑+3CO2↑生成的三聚氰胺粗品．经热水溶解，过滤，冷却结晶后制成成品．回答下列问题：（1）三聚氰胺的化学式为    （2）三聚氰胺的物理性质    ．（3）向三聚氰胺的水溶液中滴加酚酞试液，现象是    ．