牛能为人们提供的动物性食品是_______、_______。
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牛能利用农作物秸秆及农作物加工副产品酒糟等生产肉、奶等畜产品
A. 对
B. 错
奶牛品种单一化是世界奶牛业发展趋势
A. 对
B. 错
在远古的时候,人们在海边捡到一种特殊而美丽的贝壳,把它当作货币使用。汉字“贝”,就是按照这种贝壳的形状创造出来的。后来,人们不再把贝壳当作货币。A special kind of shell was collected and used as money by our ____. The _______ ‘bei’ was used to _____ the shape of the shell. Later, shells were no longer used as money.