请教一道sc题。xdf老师上课的时候一笔带过，弄不明白啊

pure最近比较烦

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

这道题为什么选A？划线前有and，首先要看有无平行，这里的extending是和谁平行？这个句子的语法结构我理地不是很清晰，求各位大牛帮忙解答一下。

ashlyzhu

extending 和spawned平行，一个v ing形式和v ed形式。。。。extend的用法就是主动表示延伸的意思。。。