某科学兴趣小组在探究“压力和物体重力之间大小关系”时，小科同学提出的猜想是：“压力的大小等于重力．”科学兴趣小组做了相关的实验．

步骤1：选用材料相同、表面粗糙程度相同、重力不同的3个物体，用弹簧测力计测出三个物体的重力；

步骤2：把3个物体依次放在水平受力面上，用专用的仪器测出3次压力大小，实验数据见表1．

步骤3：改变受力面鱼水平面的倾角，用步骤2的方法，依次测出与水平面成18°角和25°角的压力大小，实验数据见表2和表3．

请回答：

随着升学考的来临，我们的初中生活也即将结束。三年的初中生涯，总有一些难以忘怀的时刻。仔细阅读以下四段材料，从A、B、C、D中选择一个合适的标题。并完成第（2）小题。

   ①    

    Hello, I'm Tom. I remember at one time, when we were running on the playground, I was too tired to go on. As I wanted to give up, some of my classmates cheered me up. My classmates' encouragements helped me finish the run. I'll never forget it.

   ②    

    Hello, I'm Mary. When I was in Grade Two, I didn't prepare well for an English contest. I said sorry to my teacher. He said: “Any opportunity is important. You should never give it up easily.” Later on, I made good use of every opportunity. I'll never forget him.

   ③    

    Hi, I'm Lucy. The time I traveled to Qingdao with my classmates was the most unforgettable experience. We swam in the sea and caught crabs (螃蟹) on the beach. We played games and enjoyed the beautiful scenery. I will never forget that trip.

    ④   

    Hi, I'm Jim. I took part in the red song competition with my classmates last year. Every day, we rehearsed(排练) very hard in order to get a good result. Because of our hard work, we achieved a good result in the competition.

90年来，在***领导我国各族人民进行革命、建设和改革的伟大实践中，中华民族精神得到了丰富和发展，下列属于革命战争年代形成的民族精神有（   ）
①“两弹一星”精神  ②长征精神  ③雷锋精神  ④红岩精神