题目内容
为什么一般钳工用锯条烧红后置于空气中冷却即变软，并可进行加工；而机用锯条烧红后（约900℃）空冷，仍有高的硬度？
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Compared with other types of Chinese tea, _______has the most medicinal value and the least caffeine content.
Chinese tea can be classified into five basic categories according to their different processing techniques. The five types are________,________, oolong tea, compressed tea, and ________. Some minor types are white tea and yellow tea.
Black tea is so named because the tea liquid and tea leaves are _______ black.
Oolong tea is the chosen tea for the famous _______ brewing process.
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