The rain has flooded drainage canals in many orange-tree groves, which

which always modifies the nearest grammatically eligible word. So, in A and B, which modifies orange-tree groves, suggesting that orange-tree groves caused the fruit to fall; however, from the context, it is clear that flooding of drainage canals caused the fruit to fall.

p.s. Our book SC Nirvana discusses the usage of which and that, their application and examples in significant detail. If you can PM you email, I can send you the corresponding section.

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.

Meaning :
It is causal statement,
Cause -> The rain has flooded Canal in many Orange tree groves.
Effect -> Caused Fruit to Fall prematurely and Threatened to kill tree.

Sentence of the structure "Cause + "," + "Ving Modifier" " Is one of the best way to present cause and effect.

Error Analysis :
1. Relative Pronoun "Which", refers to Groves -- Making the meaning as "Groves caused the effect, instead of Flooded Canals"
2. "before it will ripen" - It is an awkward construction. Tense makes no sense, Fruit fallen in past, and "will Ripen" is indicating future tense. Illogical Tense sequence.

POE
a) which has caused the fruit to fall before it will ripen and also threatened to kill
Incorrect - Explained Above

b) which not only caused the fruit to fall without ripening, but also threatened killing
Incorrect - Which Refers to Groves

c) not only causing the fruit to fall before ripening, but also threatening to kill
Not Only X, but also Y - Idiom Is perfect.
"Causing the fruit to fell" and "Threatening to Kill" both are parallel
Correct

d) causing the fruit to fall before it will ripen, which will threaten killing
"It will Ripen " Tense error as discussed above.
"Which" - which is referring to what, it should refer to Preceding noun, So can we assume "Fruit" Even if we break the rule and assume this, still the sentence will be illogical and meaning less.
Incorrect

e) causing the fruit to have fallen before it ripened, which threatened to kill
Incorrect "Which"
"to have fallen" - Present tense referring to something happened in past.

took 50 Sec to choose option C.
POE is very easy.
A,B,D,E - Which is incorrectly used.

Experts... Correct If I am wrong

In a,b,d,e there are too many errors, some of which are highlighted in red.

In the hall, there is no need to break one's head on such a basic level question by going into several errors. The relative pronoun 'which is wrong in all the choices except in C
In A and B, which stands for the groves but it is the flooding that causes the problem. In D and E, the nearest noun is the pronoun 'it', the stepney of the noun 'fruit'.
Can the fruit threaten to kill? Therefore, C is the answer.

All other errors are of academic interest yet worth learning, but at the end of the day, let's be guided by the maxim that one percent wrong is 100 percent wrong in GMAT.

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