OG--42 关于平行

42 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

答案为A，是Spawned 和 Extending的分词的平行

关于B的解释：the ostensible parallel between extends and the idstant verb is is superficial and would result in an awkward and unclear sentence.

还是不太理解为什么不能和IS 平行。。。

请高手赐教