The study reports the newly-developed rice produces proteins that attach directly to the HIV virus. This process prevents the virus from mixing with human cells. The scientists say it can remove the effect of the virus and block its spreading.

　　The Joint United Nations Program on HIV/AIDS reports that worldwide, nearly 37 million people were living with HIV in 2017. The organization says the largest number of those are in developing countries. Nearly two-thirds of HIV cases are in Africa. Now there is no cure for HIV/AIDS though there have been developments in oral drug treatments to slow the progression of the disease.

　　The new study predicts the rice-based method will lead to long-term use of the anti-HIV treatment across the developing world. Researchers said the "groundbreaking" discovery is "realistically the only way" that anti-HIV combination treatments can be produced at a cost low enough for the developing world.

　　They say the easiest and most cost-effective way to use the rice will be to make it into a cream to be put on the skin. The HIV-fighting proteins can then enter the body through the skin. People all over the world could grow the rice and make the cream themselves. This would prevent the cost and travel required for many patients to receive treatments and medicine.

　　The process of changing the genetic structure of food crops has been debated for some time. Critics of genetically engineered crops believe they can harm people. The scientific team says further testing is needed to ensure that the genetic engineering process does not produce any additional chemicals that could be dangerous to people.

24. What does the author intend to do in paragraph 3?

　A. Stress the urgency of HIV treatments.

　B. Provide some data about HIV.

　C. Remind readers of HIV prevention.

　D. Introduce HIV to the public.

25. In which way will the rice be used at the lowest cost?

　A. By transforming it into proteins. B. By adding it to an oral drug.

　C. By attaching it to the HIV virus. D. By processing it into a cream.

26. What can we infer about the genetic engineering process?

　A. It can prevent infections of HIV. B. It can produce dangerous chemicals.

　C. It still requires perfecting. D. It applies to the developed world.

27. From which is the text probably taken?

　A. A biology textbook. B. A health magazine.

　C. A social webpage. D. A first aid brochure.

　　C

　　Cats communicate a variety of messages using cat body language. Examples include arching (弓起) their backs as a signal of fear or attack, and slowly blinking (眨) their eyes to signal relaxation. Mouth open and no teeth showed suggests a feeling of playfulness. A cat which chooses to lie on its back shows happiness, trust and comfort. Cats show dissatisfaction by moving their ears back, equal to a human frown.

　　As is the case with dogs, a twitching (抽动) tail can mean a little anger while a tail held high suggests confidence. Cats will twitch their tails when hunting or angry, while larger twitching suggests displeasure. They may also twitch their tails when playing. A tail held high is a sign of happiness, or can be used as a greeting towards humans or other cats (usually close relatives) while half-raised shows less pleasure, and unhappiness is expressed with a tail held low.

　　Some characteristic signals, however, are often misunderstood. It is important to keep in mind that each cat may show its feelings with different body language. For instance, a cat rubbing its body along an arm or leg of its owner is not only a way in which to attract attention and, perhaps, a way to ask for food; it is also a way of "marking" its owner as its own. Usually a cat with its tail held high and twitching shows excitement, but this is often mistaken for anger.

　　Many people fail or are too slow to understand the silent body language of cats. And they may have the false impression that cats are cold-hearted, unfaithful or not clever. To understand cats, people must observe a cat closely and learn what its body signals tell them.

28. Which cat body language shows that a cat is relaxed?

　A. Lying on its stomach. B. Blinking its eyes slowly.

　C. Holding its tail high. D. Moving its ears back.

29. According to the passage, a cat will twitch its tail EXCEPT ____.

　A. when it feels sleepy B. when it is hunting

　C. when it feels angry D. when it is playing

30. How many meanings does a cat's rubbing its body along its owner have?

A. 2. B. 3. C. 4. D. 5.