The verb form in the sentence is the future continuous
Either "that sounds interesting; tell me more" or "What are you talking about?"
personally, "what are you talking about?" seems condescending so I'm going to go with "That sounds interesting; tell me more"<span />
C - the legend of King Arthur - in stark contrast to the actual man - is easy to track bak to its orgins.
Both the claim and option C mention how much more difficult it is to know about the REAL King Arthur and how much easier it is to trace back the history of the legend.