Đề ôn thi Đề thi vào lớp 10 Trường Phổ thông Năng khiếu môn Tiếng Anh - Mã đề PTNK-15

An avalanche is a powerful and sudden flow of snow down a mountain slope. These events are a significant danger in snowy, mountainous regions worldwide. For an avalanche to occur, several conditions must be met. The primary factors include the angle of the slope and the structure of the snowpack. An avalanche is a natural event that (21) __________ occur in any mountainous region where there is significant snowfall, but human activity can often trigger them.

The snowpack is not a single, solid mass. Instead, it is made up of many different layers of snow that have accumulated over time. Each snowfall creates a new layer on top of the old ones. The characteristics of these layers, such as their density and temperature, can vary greatly. The most dangerous layers are often those that fell during heavy storms, sitting on top of a weaker, less stable layer beneath.

The existence of a weak layer within the snowpack is the most critical element for an avalanche. This weak layer does not bond well with the snow above or below it. It can be formed from ice, very light snow, or snow that has undergone changes due to temperature. This weak layer is unable to (22) __________ the weight of the new snow on top. This instability causes the snowpack to become a 'slab,' a large block of snow ready to slide.

The final element is a trigger. (23) __________ can be natural, like more heavy snow or wind, or it can be caused by humans, such as a skier or snowmobiler crossing a steep slope. The extra weight is often just enough to cause the weak layer to (24) __________. Once this happens, the entire slab of snow on top can detach and begin to slide down the mountain at incredible speeds.

Being aware of these conditions is essential for anyone venturing into the mountains during winter. Understanding the risks involves checking avalanche forecasts and recognizing dangerous terrain. In short, an avalanche is a combination of a steep slope, an unstable snowpack, and a trigger. Respecting the power of nature is the key to staying safe in these beautiful but potentially hazardous environments.

Imagine a time when downloading a song took ten minutes, and using the internet meant your phone line was constantly busy. This was the reality of dial-up internet, the primary way homes connected to the World Wide Web just a few decades ago. Maxing out at a sluggish 56 kilobits per second, dial-up connections relied on standard telephone lines and modems producing distinct squawks. [I]

As the internet evolved from simple text to rich graphics and streaming media, faster connections became essential. This ushered in the era of broadband, initially dominated by DSL (Digital Subscriber Line) and cable internet. DSL utilized existing copper telephone lines more efficiently for higher speeds, often reaching several megabits per second. Cable internet, leveraging coaxial TV cables, offered competitive speeds. [II] These advancements provided "always-on" internet without tying up phone lines, a significant leap towards immersive online experiences.

The true revolution in home internet came with the widespread adoption of fiber optic technology. Unlike copper wires transmitting electrical signals, fiber optic cables use thin glass strands to transmit data as pulses of light. This fundamental difference unlocks unprecedented speeds and capacities, carrying vast amounts of data over long distances with minimal signal degradation. Fiber optic connections offer symmetrical speeds and virtually eliminate latency, making gaming and high-definition streaming incredibly smooth. This engineering forms the backbone of today's fastest internet. [III]

Vietnam, in particular, has witnessed a remarkable digital transformation, moving swiftly from copper to a nationwide fiber optic backbone. State-owned enterprises like VNPT and private giants such as FPT Telecom have led this shift, investing massively in infrastructure. They systematically replaced legacy copper cables with advanced fiber optic networks, extending high-speed connectivity to urban centers and increasingly to rural areas. This rapid deployment has been pivotal for Vietnam's economic development, fostering a vibrant digital economy and connecting millions of households. [IV]

For a 14-15 year old today, slow internet is practically foreign. Your daily life—studying, connecting with friends, immersive gaming, and streaming shows—relies entirely on lightning-fast, reliable internet. This seamless digital experience, often taken for granted, is the direct result of decades of relentless innovation. From noisy dial-up modems to silent light pulses traveling through fiber optic cables, this engineering journey underpins your digital world. Understanding this evolution helps you appreciate the technology that makes your digital life possible.