Sentence Correction

39. 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

Can anyone please explain the right answer