难考点过去分词到底表被动还是表过去的时态？

过去学的语法都是:过去分词表被动，或者表示过去的时态，现在分词表示主动，或者表示进行时态，但是在ETS的解释里面，完全忽略掉过去分词表被动，现在分词表示主动，都是从时态方面来解释，好confused啊，看看这个题：

OG210. Scientists have recently discovered what could be the largest and oldest living organism on Earth, a giant fungus that is an interwoven filigree of mushrooms and rootlike tentacles spawned by a single fertilized spore some 10,000 years ago and extending for more than 30 acres in the soil of a Michigan forest.

(A) extending (B) extends (C) extended (D) it extended (E) is extending

og对于答案项(a)项的解释说'spawned refers to something that happened in the past, while extending refers to something that continues into the present.'

我知道是一个过去分词和一个现在分词并列修饰filigree。我的问题是：我不明白为什么说'spawned refers to something that happened in the past，如果是一个主动的意思发生在过去也要用过去分词吗？extending refers to something that continues into the present.
因为我个人对于分词修饰的理解是过去分词表被动，现在分词表主动。但是这里为什么是强调时态的概念？

还有很多类似的题目，有明白的能说说吗？

好问题，我也觉得按照主动被动理解更好。

不过OG没有否认你关于主动被动的说法，一般来说过去分词有两个含义：被动（如果是及物动词的话，如果是不及物动词，就没有被动意义）和表示动作已经发生；表示被动而且正在发生的动作则用现在分词被动形式--being + v-ed，而不直接用过去分词的。

不及物动词的过去分词，表动作发生在谓语动词之前的例子，可以参见OG42，从中还可以看出过去分词和现在分词的含义上的区别

OG42.  The current administration, being worried over some foreign trade barriers being removed and our exports
                        failing to increase as a result of deep cuts in the value of the dollar, has formed a group to study ways to sharpen our competitiveness.

(A)   being worried over some foreign trade barriers being removed and our exports failing

(B)   worrying over some foreign trade barriers being removed, also over the failure of our exports

(C)   worried about the removal of some foreign trade barriers and the failure of our exports

(D)   in that they were worried about the removal of
                    some foreign trade barriers and also about the
                    failure of our exports

(E)    because of its worry concerning the removal of
                    some foreign trade barriers, also concerning
                    the failure of our exports

worry about中的worry为不及物动词.

worried: adj. unhappy because you keep thinking about a problem, or about something bad that might happen

worrying: adj. something that is worrying makes you feel anxious or worried