Climbing mountains was ________, so we all felt ________.

A.tiring; tired

B.tired; tiring

C.tiring; tiring

D.tired; tired

答案及解析： A

解析：

动词加ing或ed转化成形容词，形容词时ing形式与ed形式区别在于：tiring表明“爬山”的本身是一件累人的事情，tired指人的感受。