阅读下面短文，在空白处填入一个适当的词，或填入括号中所给单词的正确形式。

    Justin is a 16-year-old boy. He is thinking about how____(spend) his money during winter vacation. He ____(save) up about 300 dollars already. He plans to buy ____computer with his money but he also wants to go skating with his friends. He can't do both ____he doesn't have enough money. What should Justin do?

    We are often in these kinds of situations. You want to see a concert ____Saturday, but it is also your mother's birthday and you do not want to let____(she) down. In this case, you don't have enough time to go to both ____(place). You must make a decision. You must think about ____should be done first. You must consider the following questions ____(serious).

    ◆Which is more important?

    ◆Which decision needs my attention more?

    ◆Which choice would satisfy me more?

    After you've answered these questions, it may be much____(easy) for you to decide what to do. So the next time you must make a decision, remember to prioritize(优先考虑).

（请你判断下列说法是否正确 ）
春秋晚期孙武所著的《孙子兵法》是世界上最早的兵书。   

世界上最长的山系是美洲板块与太平洋板块、南极洲板块相撞而形成的，它是（　　）

战国时期，秦国在成都地区修建的著名水利工程是____；秦统一后修建的沟通长江和珠江水系的水利工程是____。