Pazyryk tombs

[bolt_n_blue]

A tree’s age can be determined by counting the annual growth rings in its trunk. Each ring represents one year, and the ring’s thickness reveals the relative amount of rainfall that year. Archaeologists successfully used annual rings to determine the relative ages of ancient tombs at Pazyryk. Each tomb was constructed from freshly cut logs, and the tombs builders were constrained by tradition to use only logs from trees growing in the sacred Pazyryk Valley.
Which one of the following, if true, contributes most to an explanation of the archaeologists’ success in using annual rings to establish the relative ages of the tombs at the Pazyryk site?
(A) The Pazyryk tombs were all robbed during ancient times, but breakage of the tombs seals allowed the seepage of water, which soon froze permanently, thereby preserving the tombs’ remaining artifacts.
(B) The Pazyryk Valley, surrounded by extremely high mountains, has a distinctive yearly pattern of rainfall, and so trees growing in the Pazyryk Valley have annual rings that are quite distinct from trees growing in nearby valleys.
(C) Each log in the Pazyryk tombs has among its rings a distinctive sequence of twelve annual rings representing six drought years followed by three rainy years and three more drought years.
(D) The archaeologists determined that the youngest tree used in any of the tombs was 90 years old and that the oldest tree was 450 years old.
(E) All of the Pazyryk tombs contained cultural artifacts that can be dated to roughly 2300 years ago.

[mannu08]

IMO ans is B.

@bolt: Official Answer please.

[ramgmat]

Imo B

[manasdas]

One more vote for B..

[defylogic]

IMO B
Argument states that "the tombs builders were constrained by tradition to use only logs from trees growing in the sacred Pazyryk Valley" If B were true, this statement is further strengthened as then the archaeologists have further surety that only P.Valley wood was used.

[bolt_n_blue]

Official Answer is C.. its an LSAT open ques..
even i had marked B..

anyone who can explain C?

[defylogic]

Guys I think I got this one.
Notice that we have to find relative ages of the tombs (and not the exact age), i.e. a tomb might be 10 years older than another tomb. But how do we find this unless we have a reference point. C provides that reference point. Since all the logs have that reference point, their age difference can be successfully found.
Let's take an example
Tomb A has those 12 rings and 3 more rings aound those 12 rings.
Tomb B has those 12 rings and 5 more rings around those 12 rings.
The 12 rings give us a refernce and we can say conclusively that Tomb B is 2 years older than Tomb A (since each ring represents a year)

I must say, a very tricky question indeed.

[Nikhil Singh]

C is the only legitimate answer which uses annual rings with year patterns to explain something, hence our answer.