Đề ôn thi Đề thi vào lớp 10 Trường THPT Chuyên KHXH môn Tiếng Anh - Mã đề KHXH-87

Bluetooth is a wireless technology standard for exchanging data over short distances. It uses short-range radio waves to connect electronic gadgets without the need for cables. From smartphones and laptops to headphones and speakers, Bluetooth allows these items to communicate with each other. For a successful link, two devices (35) __________ first be 'paired' together, which is a process of mutual recognition and authorization.

Pairing is like a digital handshake. During this initial setup, the two devices agree to communicate. This one-time process creates a secure (36) __________ by exchanging a secret key. Once a pair is established, the devices can automatically reconnect in the future whenever they are close enough and turned on. The security key ensures that other nearby devices cannot listen to or interfere with the communication.

After pairing, the devices form a small, personal network known as a 'piconet'. (37) __________ allows up to eight connected devices to communicate with each other at once, with one acting as the central 'master' device and the others as 'slaves'. Once the piconet is active, the devices can begin to (38) __________ data, such as music files from a phone to a speaker, or keystrokes from a keyboard to a computer.

The technology is extremely useful for a wide range of everyday (39) __________. Think about wireless headphones, car audio systems, or computer mice. Using Bluetooth is often (40) __________ convenient than dealing with tangled wires. (41) __________ does it eliminate the mess of cables, but it also consumes very little battery power, making it ideal for portable electronics that rely on batteries for operation.

(42) __________, Bluetooth has become an essential part of modern connectivity. Its ability to create simple, low-power, and secure wireless networks between our gadgets has fundamentally changed how we interact with technology, making our digital lives more seamless and organized.

In a tropical country like Vietnam, the sun is a constant companion. It gives us light, warmth, and essential vitamin D. However, this familiar presence holds a hidden danger that many teenagers underestimate: ultraviolet (UV) radiation. While a golden tan might seem attractive, dermatologists are increasingly warning that the long-term price for unprotected sun exposure is far higher than most people realize. The risk isn't just present on bright, sunny beach days; harmful UV rays can penetrate clouds, meaning your skin needs protection even on overcast afternoons.

The primary culprits behind sun damage are two types of UV rays: UVA and UVB. Think of 'A' for Aging and 'B' for Burning. UVB rays are the main cause of sunburn, that painful, red reaction after too much time outside. UVA rays, however, penetrate deeper into the skin, leading to premature aging effects like wrinkles and dark spots. Both types contribute to the most serious risk: skin cancer. This damage is cumulative, meaning it builds up over your lifetime with every unprotected moment in the sun. The sun exposure you get as a teenager can significantly impact your skin's health decades later.

Fortunately, protecting your skin is straightforward with the right knowledge. The most common tool is sunscreen, and its effectiveness is measured by its Sun Protection Factor (SPF). An SPF of 30, for example, theoretically allows you to stay in the sun 30 times longer without burning than you could with no protection. For daily use, experts recommend a 'broad-spectrum' sunscreen with an SPF of at least 30. This ensures protection from both UVA and UVB rays. To be effective, sunscreen must be applied generously about 15-30 minutes before sun exposure, and it must be reapplied at least every two hours.

Of course, sunscreen isn't the only solution. In Vietnam, the sight of people wearing 'áo chống nắng' (sun protection jackets), gloves, and wide-brimmed hats is a testament to a deep-rooted understanding of sun safety. These items act as a physical barrier, blocking UV rays from reaching the skin. A comprehensive sun protection strategy combines these physical barriers with the correct use of sunscreen. It’s also wise to seek shade and avoid direct sun exposure during peak hours, typically between 10 a.m. and 4 p.m., when the sun's rays are strongest.

For teenagers, developing smart sun habits now is one of the best investments you can make in your future health. It’s not about avoiding the outdoors or stopping sports; it's about playing smart. By understanding the risks and using protection consistently, you can enjoy all the benefits of an active, outdoor lifestyle while keeping your skin healthy and youthful for years to come. The simple choices you make today will define the health and appearance of your skin for the rest of your life.