Dendrochronology, the study of tree-ring records to glean
information about the past, is possible because each year
a tree adds a new layer of wood between the existing
wood and the bark. In temperate and subpolar climates,
cells added at the growing season's start are large and
thin-walled, but later the new cells that develop are
smaller and thick-walled; the growing season is followed
by a period of dormancy. When a tree trunk is viewed in
cross section, a boundary line is normally visible between
the small-celled wood added at the end of the growing
season in the previous year and the large-celled spring
wood of the following year's growing season. The annual
growth pattern appears as a series of larger and larger
rings. In wet years rings are broad; during drought years
they are narrow, since the trees grow less. Often, ring
patterns of dead trees of different, but overlapping, ages
can be correlated to provide an extended index of past
climate conditions.

However, trees that grew in areas with a steady supply of
groundwater show little variation in ring width from year
to year; these "complacent" rings tell nothing about
changes in climate. And trees in extremely dry regions
may go a year or two without adding any rings, thereby
introducing uncertainties into the count. Certain species
sometimes add more than one ring in a single year, when
growth halts temporarily and then starts again.

The passage suggests which of the following about the ring patterns of two trees that grew in the same area and that were of different, but overlapping, ages?

A. The rings corresponding to the overlapping years would often exhibit similar patterns.
B. The rings corresponding to the years in which only one of the trees was alive would not reliably indicate the climate conditions of those years.
C. The rings corresponding to the overlapping years would exhibit similar patterns only if the trees were of the same species.
D. The rings corresponding to the overlapping years could not be complacent rings.
E. The rings corresponding to the overlapping years would provide a more reliable index of dry climate conditions than of wet conditions.


Friends, do you find the logic here, I think I lost somewhere! Thanks!
_________________

Find out what's new at GMAT Club - latest features and updates

A

The rings corresponding to the overlapping years would often exhibit similar patterns.

Last line of first para

Anon, can you say some more detail how you translate from "the last line of first para" to "exhibit similar patterns". So subtle, I think!
_________________

Find out what's new at GMAT Club - latest features and updates

IMO B
Keyword: different but Overlapping - ages (last sentence of first para)

Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions.

When we have "ring patterns of dead trees" (More than one) diffrent - we can correlate ages to predict the past climat condition.

But we have two trees here, one tree live and one tree dead , even though they have overlapping ages, it will not give us any information - which B says.

All other choices are not discussed in this.

I got A by POE.

B .We donot have enough information to support the answer choice because its unkown if the trees compared are alive tress or dead trees.
C. Again the passage does not discuss anything about species. So no info to support this choice either.
D.Complacent rings - steady water suppy. The questions talks about trees grown in a particular area but does not give any info about the weather conditions or water supplied to the trees.
E. The questions talks about trees grown in a particular area but does not give any info about the weather conditions.