what do you call this in english .its a stamp .it______sending lettersa 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
答
固定搭配 be used to do sth be uesd for doing sth