Đề ôn thi Đề thi vào lớp 10 Trường THPT Chuyên KHXH môn Tiếng Anh - Mã đề KHXH-72

Suspension bridges are masterpieces of engineering, famous for their elegant design and ability to span vast distances like wide rivers or bays. But how do these massive structures stay up? The secret lies in a clever distribution of forces. At its most basic, (35) __________ suspension bridge works by hanging the road from cables, which then transfer the weight to towers and finally to the ground.

The process begins with the road itself, which is called the (36) __________. This deck is where cars and people travel. The weight of the deck, and everything on it, is supported by hundreds of vertical steel cables called suspenders. These suspenders are connected directly to the deck, and they hang down from the main, much larger cables above.

The main cables are the most critical components. They stretch from one end of the bridge to the other, passing over the tops of two tall towers. All the weight from the suspender cables is transferred to these main cables, pulling on them and creating an immense force called tension. (37) __________, these cables are made from thousands of individual steel wires bundled together for maximum strength. (38) __________ the weight from the deck upwards into the main cables is the first major step in distributing the load safely.

Next, the main cables are draped over the towers. The towers' job is to (39) __________ the cables and transfer the load down to the earth. While the cables are under tension (a pulling force), the towers are under compression (a squeezing force). They must be strong enough to support the weight from the cables and push it directly into their foundations in the ground. If the main cables (40) __________, the entire structure would immediately collapse, showing how vital their connection is.

Finally, at each end of the bridge, the main cables are secured into massive concrete blocks called anchorages, which are buried deep in the ground. These anchorages are (41) __________ of the entire system, resisting the pull of the cables and keeping everything stable. An engineer once explained that the delicate balance between tension and compression (42) __________ the secret to a suspension bridge's long-lasting success.

When you think about using water, you probably picture turning on a tap to drink, wash your hands, or take a shower. But what about the water you can't see? This is often called 'virtual water', and it represents the vast amount of freshwater used in the production of the food we eat and the products we buy. The concept used to measure this is called a 'water footprint', which calculates the total volume of freshwater consumed, from growing crops to manufacturing goods, along the entire supply chain.

A country's or an individual's water footprint is composed of three different types of water. First is 'blue water', which is the water taken from surface sources like rivers and lakes, or from groundwater. Second is 'green water', which is the rainwater stored in the soil that is used by plants. Finally, 'grey water' is the volume of freshwater required to dilute pollutants to acceptable quality standards. Each of these components plays a significant role in understanding the total impact of our consumption on global water resources.

The numbers associated with our daily consumption can be astonishing. For instance, producing just one cup of coffee requires about 140 liters of water. A single cotton T-shirt has a water footprint of around 2,700 liters. The amount gets even larger for some foods; producing one kilogram of beef consumes a massive 15,000 liters of water. To put that into perspective, that's more water than most people would drink in a decade. These figures reveal the hidden water costs behind our everyday choices.

This issue is particularly relevant for Vietnam, a major agricultural exporter. The country is one of the world's leading producers of coffee and rice, both of which are highly water-intensive crops. This means Vietnam effectively exports enormous quantities of its freshwater in the form of these products. Therefore, managing this resource is vital for the country's economy and environment. It affects everything from farmers' livelihoods to national food security and is a key topic for bodies like the National Water Resources Council.

So, what can be done? While large-scale policy changes are essential, individual actions can also contribute to a more sustainable future. Reducing food waste is a powerful first step, as wasted food means wasted water. Additionally, making conscious dietary choices, such as choosing foods with a smaller water footprint like chicken instead of beef, can make a difference. By becoming more aware of our water footprint, we can all become more responsible consumers and help protect our planet's most precious resource.