一道很难抉择的阅读题gwd 5-36

sunarain

Even more than mountainside slides

       of mud or snow, naturally occurring forest

       fires promote the survival of aspen trees.

Line       Aspens’ need for fire may seem illogical

  (5)      since aspens are particularly vulnerable

to fires; whereas the bark of most trees

consists of dead cells, the aspen’s bark

is a living, functioning tissue that—along

with the rest of the tree—succumbs quickly

(10)      to fire.

      The explanation is that each aspen,

while appearing to exist separately as

a single tree, is in fact only the stem or

shoot of a far larger organism.  A group

(15)      of thousands of aspens can actually

constitute a single organism, called a

clone, that shares an interconnected root

system and a unique set of genes.  Thus,

when one aspen—a single stem—dies,

(20)      the entire clone is affected.  While alive,

a stem sends hormones into the root

system to suppress formation of further

stems.  But when the stem dies, its

       hormone signal also ceases.  If a clone

(25)      loses many stems simultaneously, the

resulting hormonal imbalance triggers a

huge increase in new, rapidly growing

shoots that can outnumber the ones

destroyed. An aspen grove needs to

(30)       experience fire or some other disturbance

regularly, or it will fail to regenerate and

spread. Instead, coniferous trees will

       invade the aspen grove’s borders and

increasingly block out sunlight needed by

the aspens.

Q36:

It can be inferred from the passage that when aspen groves experience a “disturbance” (line 30), such a disturbance

              

leads to a hormonal imbalance within an aspen clone

provides soil conditions that are favorable for new shoots

thins out aspen groves that have become overly dense

suppresses the formation of too many new aspen stems

protects aspen groves by primarily destroying coniferous trees rather than aspens

According to line line 23-28, choice A is better, but according to line 29-32, choice C is also reasonable. Which one should I prefer to?

sunarain

help! Please give me some advices!

amacd

Answer is A:

1) in C, the overly dense is not meantion in the passage..

2) line 23-28, the inbalance hormone is descirbed, then the next sentence = shows that it will fail to react so (inbalance hormone), if there is NO disturbance (fire)

An aspen grove needs to(30)       experience fire or some other disturbance regularly, or it will fail to regenerate and spread.

sunarain

:

amacd: yes.you are right!Thanks a lot!