Even more than mountainside slides of mud or snow, naturally occurring

1) C

A. qualities that make a particular organism unique
Here the author doesn't compare the qualities of Aspen trees with other trees or organisms to make it unique. He just just mentions them. So not A

B. evolutionary change undergone by a particular organism.
The author doesn't mention any stages of evolution of the Aspen plant. So not B.

C. reasons that a phenomenon benefits a particular organism
Correct answer because the first paragraph introduces the importance of the phenomenon (forest fires) and the body paragraph explains the benefits of it.

D. way in which two particular organisms compete for a resource
The author doesn't draw a comparison between two trees. He mentions coniferous trees at the last only to explain what would happen if there were no forest fires. SO not D

E. means by which a particular organism has been able to survive in a barren region
The author doesn't even mention that the trees are growing on barren lands. So not E.

2)A

A. leads to a hormonal imbalance within an aspen clone
Correct answer because the disturbance ( mainly forest fires) lead to hormonal imbalance which subsequently lead to new shoots of stems.

B. provides soil conditions that are favorable for new shoots
The author doesn't talk about soil conditions. So not B

C. thins out aspen groves that have become overly dense
The disturbance thins out Aspen groves either thin or dense or otherwise. So cannot be the thinning of only dense groves. So not C.

D. suppresses the formation of too many new aspen stems
Actually it aids the formation of new stems. So not D.

E. protects aspen groves by primarily destroying coniferous trees rather than aspens
The disturbance only destroys Aspen trees. The author never even mentions forest fires destroying coniferous trees let alone protecting Aspen trees by destroying other trees.So not E.

3)A

A. vulnerability of aspens to damage from fire when compared to other trees
Correct answer because Aspen trees have a living bark unlike most trees which succumbs to fire quickly as stated in the passage.

B. rapidity with which trees other than aspens succumb to destruction by fire
Actually the passage says the opposite about the other trees catching fire. So not B

C. relatively great degree of difficulty with which aspens catch on fire when compared to other trees
Again the passage says that Aspen trees catch fire quickly in comparison to other trees. So not C.

D. difference in appearance between the bark of aspens and that of other trees
The author doesn't talk about the appearance of the barks. So not D.

E. benefits of fire to the survival of various types of trees
The author says that fires are important for Aspen trees alone but he doesn't mention any other trees whose survival is aided by forest fires. So not E

4)D

A. Individual aspens would cease to produce hormones
The passage never mentions that the shoots would stop producing hormones. In fact it says the exact opposite. So not A

B. Individual aspens would grow outward instead of upward.
The passage doesn't talk about the direction of the growth of the grove.So not B

C. The root system of the grove's clone would die.
The passage never says that the root system would die if it doesn't regenerate. It only says that it would cease to grow new shoots.

D. The grove would lose its access to sunlight
Correct answer because if it doesn't produce new shoots, coniferous trees will invade the groves and block sunlight as mentioned in the last line of the passage.

E. Soil conditions in the grove would become unfavorable for the growth of aspens.
The author never talks about effect of regeneration on the soil conditions. So not E