四、阅读理解。
请先阅读下面短文，掌握其大意，然后根据短文内容从下面方框内的七个选项中选择五个还原到文中，使短文意思通顺、结构完整。一空一句。
Summer is here. Swimming is great exercise, and a trip to a pool or beach is a good way to have fun with family and friends. 1. It's important to stay safe while swimming. Here are a few things you can do to swim safely.
Swim only in areas set aside for swimming.
If you're on a beach near the sea, this is especially important. In some places, water runs fast, which can sweep swimmers away without warning. 2.
Be careful when diving into the water headfirst(头朝下地).
Never dive blindly(盲目地). Even though you know how deep the water is, there could be hidden dangers such as rocks that you might hit your head on. 3. Nobody knows what could happen while you are swimming. If something goes wrong, you can get help from that person as soon as possible. Time is quite important at the moment. 4.
Pay close attention to children's safety.
5. But life jackets(救生衣) alone are not enough, and an adult should always be with them.
Swim safely, and enjoy your cool summer days!
A. But swimming can also be dangerous.
B. Even a few seconds can make a big difference.
C. Swimming alone in a quiet lake is the safest way.
D. Make sure you have someone who can swim well nearby.
E. So if a sign says "No swimming", please take it seriously.
F. You should always swim immediately after eating a big meal.
G. Children who don't know how to swim should wear life jackets.

1.A 2.E 3.D 4.B 5.G

我们结合上下文逻辑逐空分析：
1. 前文介绍游泳是很棒的运动，去泳池或海滩游玩是和亲友玩乐的好方式，后文强调游泳时保障安全十分重要，前后为转折关系，A选项“但是游泳也可能很危险”可以顺畅衔接前后内容。
2. 前文提到部分海域水流速度很快，会毫无预兆地将游泳者冲走，E选项“所以如果标识写着‘禁止游泳’，请严肃对待”是前文内容顺承得出的合理结论，符合语境。
3. 后文提到如果出现意外你可以尽快从那个人处获得帮助，D选项“确保你身边有游泳技术很好的人”刚好引出后文提到的可求助对象，逻辑连贯。
4. 前文提到遇到危险时时间非常关键，B选项“哪怕只有几秒钟也会产生巨大的影响”是对“时间很重要”的补充说明，贴合语境。
5. 后文转折提到“但是仅靠救生衣是不够的，必须一直有成年人陪同”，G选项“不会游泳的孩子应该穿戴救生衣”刚好引出后文关于救生衣的转折表述，前后呼应。