A well-trained dog is more confident and can more safely be allowed a greater amount of freedom than an untrained one.
一只训练有素的狗更自信，给它更多的自由时间会比未经训练的狗更安全。
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In fact, Dowling says, a dog can have up to 225 million olfactory receptors in their nose — the part of their brain devoted to scent is 40 times greater than that of a human.