Đề ôn thi Đề thi vào lớp 10 Trường THPT Chuyên KHXH môn Tiếng Anh - Mã đề KHXH-176

Maintaining good oral hygiene is a vital part of personal care. For decades, the manual toothbrush has been a reliable tool, but technology has introduced a powerful alternative: the electric toothbrush. While both are designed to fight plaque and prevent cavities, they operate differently. The main (35) __________ between them is the power source, which affects the brushing experience and results.

An electric toothbrush works using a small internal motor. This motor powers a gear system (36) __________ causes the brush head, with its soft bristles, to move automatically. The bristles can vibrate or rotate thousands of times per minute, a speed and consistency that cannot (37) __________ by hand. This rapid motion is designed to dislodge food particles and plaque from the surfaces of the teeth and along the gumline efficiently.

Because of this automated action, many dental professionals consider electric toothbrushes to be more effective. Studies have shown that they can (38) __________ significantly more plaque than manual ones, leading to improved gum health. The cleaning process is not only more thorough but often faster, as the brush does most of the work for you. This makes them a (39) __________ option for people who struggle with manual brushing techniques.

(40) __________, many modern electric toothbrushes come with helpful features. A common one is a built-in two-minute timer, which signals when you have brushed for the recommended duration. Some also have pressure sensors that alert you if you are pressing too hard, which can damage gums. These features help guide users toward better brushing habits, ensuring that (41) __________ part of the mouth receives adequate attention.

Ultimately, the choice between an electric or a manual toothbrush depends (42) __________ personal preference, budget, and dental needs. An electric toothbrush can offer a superior clean, but a manual toothbrush, when used correctly and consistently, is also an excellent tool. The most important factor is regular brushing as part of a complete oral care routine.

On any bus in Ho Chi Minh City or walking down a busy street in Hanoi, it is a common sight: teenagers with headphones on, lost in their own world of music or podcasts. For many young people, personal audio devices are essential for daily commutes, studying, or relaxing. However, this everyday habit may carry a hidden risk. The World Health Organization (WHO) has issued a serious warning, stating that over a billion young people worldwide are at risk of permanent, avoidable hearing loss due to unsafe listening practices.

But how does this damage happen? Inside our ears are extremely delicate hair cells that vibrate in response to sound waves and send signals to our brain. When exposed to loud noises for extended periods, these hair cells can be damaged. Unlike other cells in our body, once these are destroyed, they do not grow back. The damage is often gradual and irreversible. The loudness of sound is measured in decibels (dB). While a normal conversation is around 60 dB, prolonged exposure to any sound over 85 dB—the level of heavy city traffic—can begin to cause permanent harm.

So, how loud is too loud? Many smartphones and music players can reach volumes as high as 100-115 dB, which is dangerously loud and can cause damage in less than 15 minutes of listening. A major problem, especially in urban environments like Vietnam's major cities, is ambient noise. To block out the sound of traffic and crowds, listeners often increase the volume to unsafe levels. This practice significantly increases the risk of Noise-Induced Hearing Loss (NIHL).

The initial signs of hearing damage can be subtle. Young people might experience tinnitus, a constant ringing or buzzing in their ears, or find it difficult to hear conversations clearly in noisy environments. A dangerous cycle can begin: as their hearing slightly worsens, they might turn up the volume even more to compensate, which in turn causes further damage. Many teens are unaware that the choices they make about their volume levels today could have a lasting impact on their quality of life for decades to come.

Fortunately, preventing hearing loss is straightforward. Experts recommend the “60/60 rule”: listen at no more than 60% of your device’s maximum volume for no more than 60 minutes at a time before taking a break. Investing in noise-cancelling headphones can also be a wise choice. They work by reducing external sounds, allowing you to enjoy your audio at a lower, safer volume. Ultimately, protecting your hearing is about being mindful. By making small, conscious changes now, you can ensure you continue to enjoy the sounds you love for a lifetime.