Mike is a factory worker. He is often very tired after a day's work. His wife, Jenny, has no job, so she stays at home to cook the meals. Every day he can have his dinner when he gets home from his factory.  

    One day, Mike came home very late because he was very busy in the factory. He was very hungry when he got home. He was not happy when he found his dinner was not ready. He was very angry with his wife. He shouted at her, "I'm going out to eat in a restaurant." "Wait for five minutes，" said his wife. "Why? Do you think that dinner will be ready in five minutes?" asked Mike. "Of course not," she answered. "But I can be ready to go with you in five minutes."    

图甲是A、B、C三种固体物质的溶解度曲线图．

（1）甲图中，t₂℃时，A、B、C三种物质中，溶解度最大的是____ ．

（2）t℃时，将B物质的不饱和溶液转变成饱和溶液可采取____ 　；____ （任写两种方法）．

（3）如乙图所示，20℃时，把试管放入盛有X的饱和溶液的烧杯中，在试管中加入几小段镁条，再加入5mL稀盐酸，立即产生大量的气泡，同时烧杯中出现浑浊，则X可能为A、B、C三种固体物质中的哪一种？____ ．

如图是伸肘动作的产生模式图，从图中可以看出：

我国特大、超大城市数量最多的地区是（  ）

为了实现中华民族的伟大复兴，我们必须要立足基本国情，面对主要矛盾，努力完成建设中国特色社会主义的总任务。我国现阶段的基本国情和总任务分别是（  ）
①我国正处于并将长期处于社会主义初级阶段                                  ②实现社会主义现代化和中华民族伟大复兴
③人民日益增长的物质文化需要同落后的社会生产之间的矛盾      ④把我国建设成为富强民主文明和谐的社会主义现代化国家