Anything is possible中的possible是形容词性。
It is possibly the oldest 中的为什么用副词形式?
【答】possibly 表示“也许”的意思时是一个修饰全句的副词,通常放在句首,也可以放在助动词、情态动词或者系动词be的后面。It is possibly the oldest .= Possibly it is the oldest .