It is unclear who prepared these early medallions, only that each individual box containing a medallion bore the word "Fliteline".句中的only that 应该如何理解?这是一个组合连词吗?希望解答,谢谢。
A toll-free number for tourists already in the U.S. or Canada is also available at 1-800-CALL-NYS.译文:而人已经在美国或加拿大的游客则可打免付费电话,号码是1-880-CALL-NYS。此处at是什么意思,是如何使用的?
Opera artists began using layers of masks made of oiled paper. They could peel one after another in the blink of an eye.这里的one after another是指layer还是mask呢?