Đề ôn thi Đề thi vào lớp 10 Trường THPT Chuyên KHXH môn Tiếng Anh - Mã đề KHXH-112

A wireless mouse is one of (35) __________ most common peripherals for modern computers, offering freedom from tangled cables. It allows users to control the on-screen cursor without a physical connection. This convenience is made possible by a clever system of components working together to translate physical movement into a digital command.

The process begins with an optical (36) __________ located at the bottom of the mouse. This component shines a light onto the surface, such as a desk or mousepad, and a tiny camera captures thousands of pictures per second. (37) __________, the mouse's internal processor can compare these images to determine the direction and speed of movement across the surface.

This raw movement information needs (38) __________ into a digital format that a computer can understand. The mouse's processor (39) __________ this data, converting the detected motion from the sensor into precise X and Y coordinates. This digital information is now ready to be sent.

An engineer once explained that the signal (40) __________ 'a tiny, invisible message' containing the coordinates. Instead of a cable, the mouse uses a small radio transmitter to send this data wirelessly. This whole process, from movement to transmission, happens (41) __________, ensuring there is no noticeable delay for the user.

Finally, a small USB receiver, plugged into the computer, picks up this radio signal. The receiver decodes the signal and sends the coordinate information to the operating system. If the receiver were not plugged in, the mouse movements (42) __________ any effect on the screen. The computer then updates the cursor's position, completing the seamless journey from your hand to the screen.

At first glance, the Golden Apple Snail, or Pomacea canaliculata, seems harmless. With its shiny, yellowish-brown shell, it is often found in freshwater environments. Originally native to South America, this snail has traveled far from its home and has become one of the most significant invasive alien species in Asia. In countries like Vietnam, it is not just an interesting creature but a major threat to the nation's agriculture, particularly its vital rice fields.

The snail's journey to Asia began in the 1980s. It was intentionally introduced for aquaculture, with the hope that it could be farmed as a new food source for local populations. However, due to its ability to escape from farms and its rapid reproductive rate, the snail population exploded. A single female can lay thousands of eggs in a year, making the species incredibly prolific. This characteristic, combined with its ability to survive in diverse aquatic conditions, allowed it to spread uncontrollably through rivers, canals, and into the precious rice paddies.

The primary damage caused by the Golden Apple Snail occurs in rice paddies. The snails have a voracious appetite for young, tender rice seedlings. Farmers often find their newly planted fields devastated overnight, with the green shoots eaten down to the water level. This direct consumption of the young plants severely reduces crop yield, forcing farmers to replant their fields, which costs them time and money. They are most destructive during the first few weeks after the rice is transplanted, which is the most vulnerable stage of the plant's life.

In response to this agricultural crisis, Vietnam's Plant Protection Department and local communities have implemented various control strategies. One common method is manual collection, where farmers physically remove the snails and their bright pink egg clusters from the fields. Another approach involves using biological controls, such as introducing ducks into the paddies to eat the snails. While chemical pesticides are also used, they pose risks to the environment and human health, so their use must be carefully managed. The goal is to manage the snail population, as complete eradication is extremely difficult.

The story of the Golden Apple Snail in Vietnam is a powerful lesson. It demonstrates how a single, seemingly small change—the introduction of a non-native species—can cascade into enormous environmental and economic problems. It highlights the delicate balance of ecosystems and serves as a critical reminder of the need for caution and thorough research before introducing any alien species into a new environment. The fight against this unwanted guest continues, underscoring the ongoing challenge of protecting local biodiversity and food security.