My glasses are broken .I have to buy (a new pair ).[为什么不用a new one]

问题描述:

My glasses are broken .I have to buy (a new pair ).[为什么不用a new one]

glasses是眼镜,一副眼镜是a pair of glasses
英文中的眼镜只其镜片,不可能只有一个镜片,所以是a pair ;
再说了,glasses时复数,a new one事单数,一面不能和两面相呼应,所以用a pair