战胜挫折和磨炼意志的内在动力是（    ）

中华民族是勤劳勇敢的民族，经历了许多困难和磨难，中华民族反而更强大，这是因为我们具有几千年来形成的民族精神，这就是(   )

    A poor farmer had a friend who was famous for the wonderful apples he grew. One day， his friend gave him a young apple tree and told him to take it home and 1 it.

    Seeing the gift， the farmer was very happy， and he thought he would also have a lot of wonderful apples， but when he got home， he felt 2 . He did not know where to plant it. He thought over and over and considered every place he could think of. 3 ， he decided to plant the tree in his woods. There were many high trees with thick leaves in the woods. With those trees around ，no one else could see the young apple tree. He even felt proud of himself for finding so secret a place for the apple tree. Every day he went to take care of the tree， watering it. To his surprise and 4， the apple tree didn't grow as well as he expected.  It died without sunlight and good soil.

    Later the friend asked the farmer why he had planted the tree in such a 5place. "What's the difference?" the farmer said angrily. "If I had planted the tree near the6， passers-by(行人) would have stolen the fruit. If I had planted the tree in one of my fields， my neighbors would have come at night and 7 some of the apples! If I had planted it near my house， my own children would have taken the fruits. No matter where I plant the tree， I can't have8 to enjoy the apples： So there is no difference where I planted it."

    "Yes，" said the friend. "But sooner or later someone could have enjoyed the fruit. Now you not only have robbed(抢夺) everyone of the fruit， but also have 9 a good apple tree! You don't know the true meaning of 'share'!"

    We should learn to 10in our life. The more you want to own something all by yourself， the less you get at last.

①仔细观察上述步骤的示意图，其中会影响实验结果的是甲乙丙丁戊中的____；

②这次实验操作的正确顺序是____；

③“甲丙丁戊”四个示意图中的弹簧测力计示数分别为F₁、F₂、F₃、F₄，如果关系式____成立，则可得出阿基米德原理还能测出铁块的密度ρ_铁=____（已知F₁、F₂、F₃、F₄和ρ_水）

下列物质中不能在氧气里燃烧的是（  ）