Chinese researchers have developed a new system that can gently stop hundred-ton aircraft during emergency (紧急的) landings on the runway. The system has recently received a national creation award.

The researchers developed a new material called foam (泡沫) concrete (混凝土). It looks like common concrete but weighs just 200 kg per cubic metre—about a tenth of the weight of standard concrete. When an aircraft runs into it, the material creates a “soft stopper” that takes in energy through controlled breaking. This allows the plane to slow down smoothly and finally stop safely.

Landing is one of the most dangerous periods of flight. International air travel rules require a safety area of at least 90 metres beyond runways. In the past, the area was filled with water, grass, soil, or sand. All of them had disadvantages: Water could become hard ice or attract wildlife, while soil strength changed with weather.

The key challenge is controlling how the foam concrete breaks down. It must have enough strength to support aircraft wheels but be weak enough to collapse when hit. For example, for large passenger planes, its strength must fall exactly between 0.30 and 0.35 megapascals (兆帕).

Unlike earlier foreign designs that depended on expensive but not long-lasting concrete, the Chinese team developed a method that made the system cheaper and more lasting. They also developed methods to put millions of bubbles into the material and control the way it turns hard, making sure it works well even after being used in the open air for a long time.

The system has now been used at 14 airports across China. Tests show that after one year, the material’s properties (性能) change by only 3%, proving its high quality.

1.1. What is Paragraph 2 mainly about?

A What the material looks like.

B How the material is made.

C What makes the system work well.

D How the system is developed.

解析：选C。段落主旨题。解析：第二段介绍泡沫混凝土的重量特点，讲解飞机撞击后，材料可控碎裂吸收能量，实现飞机平稳安全停下。解释系统工作的原理，是什么保障系统发挥作用。A 只提到外观，属于局部细节；文中没有讲制造过程、研发过程，排除 B、D。

2.2. What does the underlined word “collapse” most probably mean?

A Break.

B Form.

C Appear.

D Burn.

解析：选A。词义猜测题。解析：原句：材料要有足够强度支撑机轮，但受撞击时又要能够collapse。结合上文 “controlled breaking（可控碎裂）”，collapse 此处含义为垮塌、碎裂，对应 break。form 形成、appear 出现、burn 燃烧均不符合语境。

3.3. What is the key advantage of the system?

A It can stop an aircraft in a shorter time.

B It can slow down an aircraft smoothly.

C It can create a safety area of over 90 metres.

D It can be used in the open air.

解析：选B。细节理解题。解析：原文第二段 “This allows the plane to slow down smoothly and finally stop safely.” 核心优势是使飞机平稳减速。 A 文中没有提到 “用时更短”；C90 米是国际规定安全区长度，不是本系统带来的优势；旧材料如水沙土也可以露天使用，D 不是独有优势。

4.4. What is the main purpose of the passage?

A To introduce a new runway safety system.

B To explain a new flying technology.

C To describe some possible landing methods.

D To compare two different safety materials.

解析：选A。主旨写作目的题。解析：全文围绕国产新型跑道应急拦停安全系统展开，介绍材料、原理、技术难点、国内外对比、实际应用。B 不是飞行技术，是跑道地面安全系统；C 没有介绍多种降落方式；对比国外材料只是文中部分内容，并非写作目的。