Đề ôn thi Đề thi vào lớp 10 Trường Phổ thông Năng khiếu môn Tiếng Anh - Mã đề PTNK-180

Have you ever wondered why our year has 365 days, but a year on another planet might be much shorter or longer? The answer lies in basic celestial mechanics. A planet's 'year' is the time it takes to (21) __________ one full journey, or revolution, around its star. This period is determined by the planet's orbit—the path it follows through space. Each planet in our solar system travels around the Sun, but not all of them take the same amount of time to finish their trip.

Let's take our home, Earth. Its orbit around the Sun is a very long journey. The time it takes for Earth to travel this entire path is approximately 365.25 days. (22) __________ is what we define as one Earth year and why we add a leap day to our calendar every four years. This concept of a year is entirely based on our planet's movement through space, a fundamental cycle of time for us.

Now, consider other planets. Mercury, the planet closest to the Sun, has a much smaller orbit. Because its path is shorter, its year is only 88 Earth days long. In contrast, Mars is farther from the Sun than Earth is. Consequently, Mars's orbit is larger, and it has a longer journey to make. A year on Mars is much longer, lasting about 687 Earth days, which is almost twice as long as Earth's year.

(23) __________ does the orbital path get larger for distant planets, but their travel speed also decreases. They move more slowly due to the star's weaker gravitational pull. Therefore, they have to (24) __________ a greater distance at a slower speed. For this reason, we must conclude that a planet's distance from its star is the most important factor that influences the length of its year.

In conclusion, the length of a 'year' is unique to each planet because of its position. The specific path a planet follows around its star, called an orbit, and the speed at which it travels, both depend on this position. From the swift 88-day year of Mercury to the nearly two-year-long journey of Mars, each planet's calendar is a unique result of its place in the solar system.

We all know water is vital for daily life. But have you ever considered the 'hidden' water in your food or clothes? This isn't the water you see, but the astonishing amount used during production. For instance, that cup of coffee you enjoy needs about 140 liters of water, from growing beans to processing them. This unseen consumption is measured by a 'water footprint,' a crucial concept for understanding our impact on the planet’s most precious resource.

A water footprint represents the total freshwater volume used to produce an item or service, categorized into 'green' (rainwater), 'blue' (surface/groundwater), and 'grey' (to dilute pollutants) types. Understanding this reveals true environmental costs. [I] For instance, a single kilogram of beef requires over 15,000 liters, and a kilogram of rice, a common staple, uses around 2,500 liters. Even a chocolate bar can have a footprint of 1,700 liters. [II]

Globally, understanding water footprints is more critical than ever. [III] Freshwater resources are finite, yet demand is constantly rising due to population growth, industrialization, and changing consumption. Regions worldwide face water scarcity, impacting agriculture, ecosystems, and human well-being. Climate change worsens this, altering rainfall patterns and increasing droughts. By mapping water footprints, we can identify inefficient and unsustainable practices, paving the way for better water management and more responsible resource use on a planetary scale.

For countries like Vietnam, where agriculture is a cornerstone of the economy, the water footprint concept is particularly relevant. As a major global exporter of crops such as rice and coffee, Vietnam's agricultural practices carry a large hidden water cost. The National Water Resources Council, alongside other bodies, actively implements strategies for sustainable water management. This is vital not only for national food security but also for maintaining the ecological balance of crucial river deltas and coastal areas, vulnerable to climate impacts and water-intensive industries.

So, what does this mean for you, as a 14 or 15-year-old? Every choice, from what you eat to what you buy, has an invisible water impact. Opting for less water-intensive foods, reducing food waste, and choosing products from sustainable sources can collectively make a significant difference. Being aware of 'hidden water' empowers you to become a conscious consumer and a proactive advocate for water conservation. Understanding your water footprint isn't just academic; it’s a step towards safeguarding our planet’s most precious resource for your generation and those to come. [IV]