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最根本的强化物是初级强化物。
And basically, there are primary reinforcers.
youdao
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氟化物可以强化生长中的牙齿，这是已证明的事实。
It is a proven fact that fluoride strengthens growing teeth.
《牛津词典》
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氟化物可以强化生长中的牙齿，这是已证明的事实。
It is a proven fact that fluoride strengthens growing teeth.
《牛津词典》