a LR question

chasingd2012

原题是: Mature white pines intercept almost all the sunlight that shines on them. They leave a deep litter that dries readily, and they grow to prodigious height so that, even when there are large gaps in a stand of such trees, little light reaches the forest floor. For this reason white pines can't regenerate in their own shade. Thus when in a dense forest a stand of trees consists of nothing but mature white pines, it is a fair bet that_____

Which one of the following most logically concludes the argument?

正确选项是(A): the ages of the trees in the stand don't differ from each other by much more than the length of time it takes a white pine to grow to maturity.

但不太明白这个选项为什么对，是怎么一个关系？

simonshen

这题的题目里说mature 的white pine会阻挡住阳光，并且长得很高，因此使得树林的低矮处见不到阳光，因此如果white pine长在一起的话肯定都是差不多同时栽下去，同时成熟长高的。因为如果在一起的white pine，先种一些让他们成熟，他们就会长得很高遮住阳光，然后在这些树木成熟后，再新种的white pine因为很矮，在低处就得不到阳光不可能生长了。所以如果white pine种在一起的话，他们之间树龄的差距应该不会大于其中一些树长成年的时间。