Do you know that the sweeteners in your favorite drinks may do more than just add sweetness? A new study from Cambridge University shows they can affect the bacteria living in our gut. These tiny organisms play an important role in keeping our body healthy.

Sweeteners are widely used in many foods and drinks. You can find them in soft drinks, candies, desserts, and snacks. They are often marketed as healthier choices than sugar. However, scientists are finding more evidence that they may be linked to health problems such as obesity and diabetes. These health problems may be connected to changes in gut bacteria.

In this study, researchers tested 39 different sweeteners in the lab. They grew 25 types of gut bacteria and exposed each type to the sweeteners. The results showed that about three-quarters of them changed how at least one type of bacteria grew. Some sweeteners even slowed down or stopped the growth of bacteria that are important for a healthy gut.

The study also looked at what happens when sweeteners are mixed with other common substances. In over 100 cases, the effects changed. Some combinations made the effect stronger, while others made it weaker. For example, a sweetener made from stevia (甜菊) plant was combined with a common medicine used for depression. Together, they strongly reduced the growth of two important gut bacteria. The mixture also appeared to affect cells that play a role in the body’s immune responses.

1.1.The phrase “These tiny organisms” in Paragraph 1 refers to ________.

A the scientists

B the bacteria

C the sweeteners

D health problems

解析：选B。B词义指代题。短语“These tiny organisms”出现在第一段第二句，该句是对前一句的进一步说明。前一句提到甜味剂会影响“the bacteria living in our gut”（我们肠道中的细菌），紧接着用“These tiny organisms”来指代这些细菌，并说明它们在保持身体健康方面的重要作用。因此，“tiny organisms”指的就是“bacteria”。A项“科学家”、C项“甜味剂”和D项“健康问题”都与该指代关系完全无关，无法在上下文中找到对应。故选B。

2.2. How are sweeteners usually promoted to consumers?

A They are healthier choices than sugar.

B They may lead to diabetes and obesity.

C They are less popular than natural sugar.

D They can only be used in soft drinks.

解析：选A。A细节理解题。题干问的是甜味剂通常被如何推销给消费者。第二段明确提到“They are often marketed as healthier choices than sugar.”（它们通常被宣传为比糖更健康的选择），与A项表述完全一致，因此A项正确。B项提到的“可能导致糖尿病和肥胖”是文中科学家发现的潜在健康问题，并不是商家用来吸引消费者的宣传说法；C项“不如天然糖受欢迎”在文中并未提及；D项“只能用于软饮料”则与第二段首句“widely used in many foods and drinks”相矛盾，甜味剂的用途远不止软饮料，因此这三项均可排除。故选A。

3.3. What is one major finding of the study?

A Sweeteners are safe.

B Sweeteners killed all bacteria.

C Sweeteners are important for a healthy gut.

D Sweeteners change the bacterial growth.

解析：选D。D细节理解题。根据第三段，研究人员测试发现“about three-quarters of them changed how at least one type of bacteria grew”（大约四分之三的甜味剂改变了至少一种细菌的生长方式），有的甚至减缓或阻止了对健康肠道有重要作用的细菌的生长。这直接说明甜味剂会改变细菌生长，故D项正确。A项“甜味剂是安全的”与研究结论相反，研究表明甜味剂有潜在影响；B项“甜味剂杀死了所有细菌”夸大其词，文中仅提到部分甜味剂抑制了某些细菌，并非杀死全部；C项“甜味剂对健康肠道很重要”属于张冠李戴，文中强调的是那些肠道细菌本身对健康重要，而非甜味剂，甜味剂反而可能抑制它们。故选D。

4.4. What is Paragraph 4 mainly about?

A The danger of mixing stevia with medical drugs.

B How mixtures of sweeteners produce varied effects.

C Different kinds of widely used medical substances.

D Ways to reduce the influence of sweeteners.

解析：选B。B主旨大意题。第四段首句为该段的主题句：“The study also looked at what happens when sweeteners are mixed with other common substances.”（研究还观察了甜味剂与其他常见物质混合时会发生什么。）接着指出在超过100种混合情况下效果发生改变，有的增强，有的减弱，并用了甜菊甜味剂与抗抑郁药混合的例子来具体说明这种不同效果。整个段落围绕“甜味剂混合物会产生不同效果”这一中心展开，因此B项概括准确。A项“混合甜菊与药物的危险”仅仅是段落中的一个具体例子，无法概括全段；C项“各种广泛使用的医疗物质”偏离段落中心，医疗物质只是混合实验中涉及的一方；D项“减少甜味剂影响的方法”在文中完全没有提及，属于无中生有。故选B。