Sentence Correction (SC) | Re: The rain has flooded drainage canals in many orange-tree gro

Hi,

Kindly help me understand this question!

The rain has flooded drainage canals in many orange-tree groves,which has caused the fruit to fall before it will ripen and also threatened to kill the trees.

a)which has caused the fruit to fall before it will ripenand also threatened to kill
b) which not only caused thefruit to fall without ripening , but alsothreatened killing
c)not only causing the fruit to fall before ripening, but also threatening to kill
d) causing the fruit tofall before it will ripen