将海水淡化是一项海洋开发工程。（  ）

15后面接着的一个数是____。

阅读下面短文，从短文后各题所给的四个选项(A、B、C和D)中，选出一个最佳选项。   
    “Daddy, can I have a piece of cake？” my oldest son asked me.
We had just been to the gym and stopped to eat at the restaurant.
    “No，” I replied, “you don't need a piece of cake.”
My son 1 15 in a few days. He 2  over 6 feet tall. He is very slim and athletic in shape . It was not always that way. My wife wrote a book about the challenge and   3   of getting him fit. He now takes it  4  and looks as if he's never been overweight in his life.
    He had a full plate of vegetables and tofu.  He didn't need a piece of cake.  5 ， everything in the restaurant is quite  6 . Our dinners could have  7 a family of seven at a fast food restaurant. That cake probably  8 $5.
    He was silent as he looked at the delicious cakes. I had forgotten that I had walked over to the cake shelf while he was   9 his food from the buffet (自助餐)．
    I looked at my plate. There sitting on the edge was a piece of 10. I looked at it wondering but also knowing how it got there. “We will divide it，” I said.
    A few days later my oldest son was  11me again. We stopped at a   12  . He ordered a sandwich. I then13 two sandwiches. He immediately barked, “Can I have two？” He wanted 14what Daddy had.
    Your kids are very   15 to put on their trays, exactly what you have on yours, and I think this applies to (适用于) more than food. Keep your life plate with only what you want your kids to have.

数 $\sqrt{3}$ 的相反数是____．

瑞典化学家诺贝尔研制炸药屡遭失败，甚至为此失去亲人，但他矢志不移，终于获得成功。这说明了（　　）