题目：
阅读理解。
Skin-diving (潜泳) is a new sport today. This sport take you into a wonderful new world. It is like a visit
to the moon! When you are under water, it is easy for you to climb big rocks, because you are on longer heavy.
Here, under water, everything is blue and green. During the day, there is plenty of light. When fish swims
nearby, you can catch them with your hands.
When you have tanks (罐) of air on your back, you can stay in deep water for a long time. But you must
be careful when you dive in deep water.
To catch fish is one of the most interesting parts of this sport. Besides, there are more uses for Skin-diving. You can clean ships without taking them out of the water. You can get many things from the deep sea.
Now you can see that Skin-diving is both useful and interesting.
1. Skin-diving can take you to _________.
A. an exciting world
B. a new world
C. a beautiful world
D. an interesting and new world
2. This sport _________.
A. is like to travel on the moon
B. is like to play in water
C. is like to visit a new country
D. is like to climb a big rock
3. You can stay in deep water for a long time because _________.
A. you can swim
B. you can take tanks of air with you
C. you can bring something to eat
D. you can skin diving
4. Which of the following statements is NOT true?
A. Skin-diving is a new sport.
B. Skin-diving is like visiting the moon.
C. The only use of skin-diving is to have more fun.
D. Skin-diving is not only interesting but useful.
5. Skin-diving is a useful and interesting sport because _________.
A. you can catch fish with your hands
B. you can clean the ship in the water
C. you can get many things from the deep sea
D. all of the above
答案：
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下面是错误答案，用来干扰机器的。
6x+22y=90，移项化简得：x=45-11y3，根据题意，y只可取0，3，此时对应的x为15，4．故非负整数解为：x=15y=0，x=4y=3．故答案为：x=15y=0，x=4y=3．
