Most people know that drinking water is good for the body. It helps your skin, supports exercise, and can prevent headaches. But staying hydrated is just as important for your brain and your mood. Even losing a small amount of water can change how you feel and think.

Your brain is about 75% water, so it is very sensitive to fluidloss (液体流失). When you don’t drink enough, nerve (神经)signals slow down and your brain has to work harder. This can make you feel tired, easily annoyed, or foggy. Scientists have found that losing just a little body water can already upset your mood. If the loss grows larger, around 2%, it can become harder to pay attention and solve problems.

Some people feel these effects soonerthan others. Older adults and young children are more at risk. People taking certain medicines or those working in hot places may also notice mood changes earlier. After hard exercise, even a small fluid loss can quickly affect how you think and feel.

1.1. The underlined word “hydrated” in Paragraph 1 is closest in meaning to “______”.

A full of energy

B with enough water

C doing exercise

D eating healthy food

解析：选B。B词义猜测题。文章第一段先讲喝水对身体有好处，接着用“But staying hydrated is just as important for your brain and your mood.”转折，强调保持“hydrated”对大脑和情绪同样重要，后文则围绕身体缺水会影响情绪和思维展开。可见“hydrated”与体内水分是否充足密切相关，因此选B“with enough water”（水分充足）。选项A“精力充沛”是水补充后的结果，并非词义本身；选项C“做运动”和选项D“吃健康食物”均与水分无关，故排除。故选B。

2.2. How might you feel when your body loses water?

A You feel worn out and upset.

B Your muscle works faster.

C You are more focused.

D You are happy and calm.

解析：选A。A细节理解题。第二段明确说明缺水会让人“feel tired, easily annoyed, or foggy”，也会“upset your mood”，这些感受与选项A中“worn out and upset”（疲惫心烦）完全吻合。选项B“肌肉工作更快”和选项C“更专注”在文中均未提及，而且实际上缺水会让人更难集中注意力；选项D“开心平静”与缺水带来的烦躁、疲倦完全相反，因此不能选。故选A。

3.3. Which of the following people would probably feel the effects the earliest?

A A healthy young man resting at home.

B A child playing in a cool classroom.

C An old woman taking medicine daily.

D An adult walking slowly in a park.

解析：选C。C细节理解题。第三段指出，“Older adults and young children are more at risk”，并且“People taking certain medicines... may also notice mood changes earlier”，可见老年人和长期服药的人会最早感受到缺水的影响。选项C“一位每天吃药的老年女性”同时符合“老年人”和“服药”两个高风险特征，因此最可能最早感受到影响。选项A“在家休息的健康年轻人”属于低风险人群；选项B“在凉爽教室玩耍的孩子”虽然是儿童，但环境凉爽，且未叠加其他易感因素；选项D“在公园慢走的成人”也不在文中提到的易感群体中，因此这三类人都不会比选项C更早受到影响。故选C。

4.4. What can we infer from the last paragraph?

A Drinking water slowly works better.

B Only water-rich foods can hydrate you.

C Over 10 cups of water are needed daily.

D A water bottle is hard to carry.

解析：选A。A推理判断题。最后一段建议“Drink a little throughout the day”，即一天中分多次少量饮水，由此可以推断，持续、缓慢地补充水分比一次性大量喝水更能保持身体水分平衡，也就是“慢慢喝效果更好”，故选A。选项B夸大了事实，文中只是说吃富含水分的食物有帮助，并未说“只有”这些食物才能补水；选项C将“8到10杯”的建议绝对化为“必须超过10杯”，与原文不符；选项D与文意相反，作者建议带水瓶，显然不认为水瓶很难携带。故选A。

5.5. What is the best title for the passage?

A How to Exercise in Hot Weather

B Tips for Solving Brain Problems

C The Importance of Eating Fruit

D Water and Your Changing Feelings

解析：选D。D主旨大意题。全文围绕“水与情绪、思维的关系”展开：开篇点出“staying hydrated is just as important for your brain and your mood”，接着讲缺水如何让人疲劳、易怒、注意力下降，再说明补水后情绪和注意力能恢复，最后给出保持水分的建议。选项D“水与你变化中的情绪”准确概括了这层核心意思。选项A“如何在热天锻炼”只涉及文中一处细节；选项B“解决大脑问题的建议”范围过宽，文章专门讲的是水分对大脑和情绪的影响，而非泛泛的大脑问题解决方法；选项C“吃水果的重要性”仅出现在最后的建议部分，不能涵盖全文。故选D。