问题描述：
what do you call this in english .its a stamp .it______sending letters
a is used to b is used for 为什么选 b
而computer are used to control not only the speed but also the direction of the spaceships是用used to
a is used to b is used for 为什么选 b
而computer are used to control not only the speed but also the direction of the spaceships是用used to
问题解答：
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