00 21. Rescue dogs are real heroes because they go to dangerous places to save people’s lives. However, becoming a professional rescue dog is not an easy journey for any puppy. First, during the early stage of training, trainers must 111 (21) the puppies behave themselves and follow simple orders. Not every dog can be a rescue dog; they must 22. brave and stay calm even when they hear loud noises or see fire. During the difficult training months, trainers 23. the dogs jump over high walls, walk through broken (破的) buildings, and find hidden (隱蔽的) people in dark, scary places. A rescue dog’s nose is much more sensitive (靈敏的) than a human’s, so it can smell someone far away. When a dog finally finds a hidden person, it must bark loudly to 24. the trainers hear it from a distance (距離). Although this work is very hard and tiring (厭煩的), it makes the dogs 25. much more useful and important than common (一般的) pets. Training takes a long time and lots of hard work, but once they finish the lessons, these dogs are ready to protect us. 21.

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