You've both been very impressive today.
请问both为什么放在这里啊,是什么词性什么成分?
both是代词,作You的同位语。You've both been very impressive today.=You have both been very impressive today.这里的 have 是助动词,been 是系动词,是主要动词, both 放在助动词和主要动词之间,属于正常位置。