A：Welcome to the Zhoukoudian caves here in China. It is 61._____ great pleasure to meet you students from England，who are interested in archaeology. You must be aware that it’s here 62._____ we found evidence of some of the earliest people who lived in this part of the world. We’ve been excavating here for many years and...S1：I’m sorry 63._____ (interrupt) you but how could they live here? There are only rocks and trees.A：Good questions. You are an acute 64._____(observe).We have found human and animal bones in those caves high