Long ago, a wolf called Howler lived in a valley where lots of fruit trees grew. He often tried to climb up the trees to eat the fruit, but couldn't reach.

    In the valley, an old man named Martin also had a few fruit trees that he looked after very well. But as he was getting older, he noticed that he didn't have the strength to pick the fruit.

    Martin had the most beautiful fruit trees in the valley, which was why Howler had his eye on them. One day he decided to steal the fruit and started jumping up and down the tree.

    Martin looked out of the window and realized that the wolf was trying to steal fruit from his beautiful trees. Howler jumped and jumped, but he couldn't reach even the lowest branches of such a big tree.

    Seeing this, Martin had a great idea: he offered Howler a ladder to climb up, but in return the wolf would have to give him half of the fruit. Howler accepted the deal and began to collect the fruit. For the whole morning, he went up and down the ladder filling his basket with the fruit.

    Howler soon realized that he could eat all the fruit if he didn't give Martin some. He thought up a new and secret plan. Martin, on the other hand, trusted Howler and even began to think they would be friends forever.

But the wolf stole the ladder and went off to other trees in the area for more fruit.

    Realizing that the ladder was missing, Martin went looking for it. Martin felt very disappointed at the trick and no longer trusted Howler. Though he wasn't angry with the wolf and they became friends again, he never made any more deals with him.

    At last, Howler learned that he shouldn't trick people and he should keep promises. He also learned that if he had been honest and not greedy, he would still have been able to enjoy more delicious fruit.

氢气是未来最理想的能源，科学家最近研制出利用太阳能产生激光，并在二氧化钛（TiO₂）表面作用使海水分解得到氢气的新技术2H₂O2H₂↑+O₂↑．制得的氢气可用于燃料电池．试完成下列问题：

太阳光分解海水时，实现了从____ 能转化为____ 能，二氧化钛作____ 生成的氢气，用于燃料电池时，实现____ 能转化为____ 能．分解海水的反应属于____ 反应（填“放热”或“吸热”）．