Đề ôn thi Đề thi vào lớp 10 Trường Phổ thông Năng khiếu môn Tiếng Anh - Mã đề PTNK-86

The construction of a spider's web is one of nature's most impressive engineering feats. A spider creates its web using a special protein-based silk, a material that comes from its spinnerets, which are special organs on its abdomen. This silk is not only strong but also incredibly flexible, allowing the web to withstand wind and the struggles of trapped insects. The entire process follows a logical and predictable sequence of steps, resulting in a structure that is both beautiful and highly functional for catching prey.

The process (21) __________ when the spider releases a single, thin thread of silk into the wind, hoping it will catch onto a distant object like a branch or a leaf. This first thread, known as the bridge line, is incredibly light but strong. Once the end of the thread attaches to a surface, the spider pulls it tight and secures it, forming the first foundation of its new home. This initial step is critical and depends heavily on air currents.

Next, the spider walks carefully across the new bridge line, often reinforcing it with a second or third thread to make it stronger. From the center of this bridge line, it drops another thread downwards, attaching it to a lower point to create a 'Y' shape. This forms the first three radial lines of the web. (22) __________, the spider proceeds to build the outer frame and adds more radial lines, which spread out from the center like the spokes of a wheel.

With the frame and radial lines complete, the spider begins to spin a temporary, non-sticky spiral. This auxiliary spiral starts from the center and moves outwards, acting as a guide and providing stability during construction. It is not very (23) __________ at trapping insects. Once this is done, the spider starts its journey again from the outside edge, this time laying down the capture spiral, (24) __________ is coated with a sticky substance designed to catch prey. As it lays the sticky line, it removes the temporary spiral.

Finally, with the intricate structure complete, the spider will often sit in the center of the web or hide nearby, keeping a close watch for the vibrations made by an insect caught in the sticky threads. The web is not just a trap but also a complex communication system, telling the spider the size and location of its next meal. This remarkable process showcases the spider's innate ability as a master builder, turning simple silk into a sophisticated tool for survival.

Walk into any trendy café in Vietnam or scroll through social media, and you'll likely spot them: houseplants. From delicate ferns to towering monsteras, these green companions are a staple in modern décor, especially in cities like Hanoi and Ho Chi Minh City where urban air quality is a common concern. Many, perhaps even you, have embraced this trend, believing these leafy friends not only beautify but also act as tiny, natural air purifiers. But is this popular idea rooted in science, or just a pleasing myth? [I]

The belief in plants' air-cleaning prowess largely stems from a groundbreaking NASA study in the late 1980s. Aiming to purify air in sealed spacecraft, researchers investigated common houseplants. Their findings were impressive: certain plants removed significant amounts of airborne volatile organic compounds (VOCs) like formaldehyde, benzene, and trichloroethylene from controlled, sealed chambers. This research provided the initial scientific backing for the widespread claim that plants could be effective biofilters. [II]

However, the NASA study conditions were far removed from a typical room. Experiments used small, sealed chambers with high pollutant concentrations. In a real home, rooms are vast, air circulates freely, and new pollutants emerge constantly. For plants to significantly impact air quality, you'd need hundreds of them, not just a few on your windowsill. This context is crucial when applying lab results to everyday environments. [III]

While not the super-efficient air filters some hope for, houseplants still offer undeniable benefits. They can subtly increase humidity, beneficial in dry environments. More importantly, studies consistently show that having plants indoors improves mood, reduces stress, and boosts overall well-being. They add a calming aesthetic, create a more natural feel, and can even slightly reduce dust. So, while some shops might promote purifying qualities, their true value often lies more in positive psychological and visual impact.

So, can your houseplant truly clean your room's air? Science suggests their direct impact on purifying large volumes of air in a typical home is minimal compared to mechanical air filters. They aren't tiny, efficient VOC scrubbers. [IV] Plants enhance our spaces, connect us with nature, and undeniably contribute to a healthier, happier environment in other, equally valuable ways. Embrace your green companions for the joy and calm they bring; their true magic might be for your well-being, not solely for your air quality.