Đề ôn thi Đề thi vào lớp 10 Trường THPT Chuyên KHXH môn Tiếng Anh - Mã đề KHXH-33

Have you ever wondered how you can run, jump, or even just smile? All these actions are possible thanks to our muscular system. This complex network allows us to (35) __________ a huge variety of movements, from lifting heavy objects to blinking our eyes. These are our voluntary muscles, which we control consciously. Our brain sends signals along nerves, telling these muscles when to act.

Each muscle is made of thousands of tiny strands called muscle fibers. When a muscle receives a signal from the brain, its fibers shorten, or contract. This contraction creates a pulling force. It’s important to remember that muscles can only pull; they cannot push. To create movement, they must work with bones and joints, pulling on them to move parts of the body. This is (36) __________ fundamental principle of biomechanics.

Because muscles can only pull, they must work in pairs to create movement in opposite directions. (37) __________, when you bend your arm, your bicep muscle contracts and pulls your lower arm up. At the same time, its partner muscle, the triceps, relaxes. To straighten your arm, the opposite happens. The triceps contracts and the bicep relaxes. They need to (38) __________ each other to allow for smooth motion.

Besides voluntary muscles, we also have involuntary muscles that work automatically. Your heart, for instance, is a powerful muscle that works without you thinking about it. It has to keep pumping blood to all parts of your body, so it truly has to (39) __________. Our body depends on these muscles to continue (40) __________ even when we are asleep.

A fitness expert once explained that a client asked him how he (41) __________ so strong. He told them it was all about understanding these muscle pairs. If we did not have muscles working together in pairs, every movement (42) __________ much more difficult and less controlled. This clever system of contracting and relaxing partners is what gives us the ability to perform everything from simple gestures to complex athletic feats.

Imagine scrolling through social media and seeing a video of your favorite singer endorsing a product you’ve never heard of, or a famous politician saying something truly shocking. You watch it again. It looks completely real. The voice, the facial expressions, everything seems perfect. But is it? Welcome to the era of deepfakes, a technology that uses artificial intelligence (AI) to create highly convincing but entirely fake videos and audio. As this technology advances, the line between reality and digital fabrication is becoming dangerously blurry.

Deepfake technology works by training an AI on a massive dataset of images and audio of a specific person. The AI learns their facial movements, voice patterns, and mannerisms, allowing it to generate new content where that person appears to say or do things they never did. What was once a complex process requiring powerful computers is now becoming more accessible, with some apps allowing users to create simple face-swaps. While often used for harmless fun or in the film industry to create special effects, this sophisticated technology also carries significant risks.

The potential for misuse is enormous. Deepfakes can be a powerful tool for spreading misinformation and fake news, potentially influencing public opinion or damaging someone's reputation. A more direct threat, which is now a growing concern in Vietnam, is their use in financial scams. Cybersecurity experts, such as the well-known Ngo Minh Hieu (HieuPC), have started public campaigns to raise awareness. Scammers can use AI to clone a person's voice from a short audio clip, then call their family members pretending to be in trouble and asking for money. Because the voice sounds so authentic, they can easily trick unsuspecting relatives.

So, how can you protect yourself in a world where seeing isn't always believing? The first step is to become a more critical viewer. Pay close attention to details in videos. Do the person's eyes blink unnaturally, or do they stare without blinking for too long? Is the lighting on the face consistent with the background? Does the skin texture look too smooth or blurry? Sometimes, the audio is a giveaway; the voice might sound robotic or lack emotional variation.

Beyond visual clues, the most powerful defense is verifying the source. Ask yourself: where did this video come from? Was it posted by a reputable news organization or an anonymous social media account with no history? Before you share something shocking, take a moment to search for it on reliable news websites. If a major story is real, established journalists will be reporting on it. In this new digital landscape, questioning what you see online is not just a good habit—it's an essential skill for staying safe and informed.