Yeah I am so happy. Did you happen to choose C? I dont blame you if you did because I did type C before I changed my mind.
The argument is talking about a particular civilization, not some other ancient civilization that existed there before or not something that came later. If this happens then it is possible that there is a mixup of few things that were used earlier. If you show something that casts doubt on the originality of the artifacts or the timber then in effect u have questioned the argument.
A says the timber bore marks used by earlier settlement meaning the timber is not original to the civilization under question ( Well u can refute this as well but not very strongly because u are looking for uniqueness of recovered things that distinguish different civilizations )
C is close because u can say that the tests that determine the age of timber may not be accurate because they are old compared to new tests that determine the age of pottery. You cannot conclusively say this.
Well actually, I chose D, because I thought tthat it can provide better generalization for the older conclusion. (There is only one piece of new evidence cited in the passage).
Anyhow your explanationmake sense. But I think it is very vague.
I removed A because I considered the settlement mentioned in the passage and the one mentioned in the A same. Which actually lead to conclusion that both theories (new and old) are wrong but I did not pay much attention to that.