210. 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
Choice A, the best answer, preserves grammatical parallelism while allowing for logical expression of temporal relationships; A employs the parallel participial phrases spawned... and extending ... to modify filigree. Other choices present different grammatical constructions that are not participial modifiers and thus not parallel to spawned: extends in B is a present-tense verb; it extended in D begins a new clause; and is extending in E ungrammatically introduces a new predicate. In C, extended is nonparallel if it is assumed to be a past tense verb form; if it is assumed to be a past participle, it illogically states, as does D, that the filigree extended only in the past.
一路看了很多关于这题的讨论下来，对于题目的答案没有疑问。但是对于OG上的红色部分的解释存在些许疑惑
以前判断是用过去分词还是用现在分词最好的方式就是判断是主动还是被动，而这里OG的解释中加入了关于判断时态的元素，是说过去分词表示已经完成，而用现在分词表示还在进行的状态。
那么我想请问，如果我想表达的是主动的已经完成的动作，是用过去分词还是现在分词呢？还是根本就没有这样的状态存在呢？
实在是很困惑！忘指教！究竟是主动被动的判断重要，还是时态的判断重要呢？ | 
