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!

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

我们逐空结合上下文逻辑分析：
1. 空前介绍游泳是很好的运动，和亲友去泳池/海滩游玩很有乐趣，空后点明游泳时保障安全十分重要，此处需要转折引出游泳的危险性，对应A选项。
2. 空前说明部分水域水流速度很快，会毫无预兆冲走游泳者，顺承得出要严肃对待“禁止游泳”标识的结论，对应E选项。
3. 空后提到如果发生意外可以立刻从他人处获得帮助，对应“确保附近有游泳技术很好的人”的D选项。
4. 空前强调意外发生的瞬间时间非常关键，对应“哪怕短短几秒钟都能产生巨大影响”的B选项，逻辑衔接通顺。
5. 空后转折说明仅靠救生衣是不够的，还需要成人全程陪同，对应“不会游泳的儿童应当穿戴救生衣”的G选项，前后内容呼应。
剩余C、F是不符合游泳安全常识的错误表述，和全文逻辑不符，直接排除。