Since the 1940's the farms and ranches of the Great Plains

Question

Since the 1940's the farms and ranches of the Great Plains have been supplied with water from the Ogallala aquifer; this underground reservoir contained an estimated quadrillion gallons of water,  which equal Lake Huron , but now reserves are becoming depleted.

A) which equal Lake Huron
B) which equal Lake Huron's
C) equal to Lake Huron's
D) the equivalent of Lake Huron's
E) the equivalent of Lake Huron

Kindly specify the reasons for your answer.
Sunil

asaf · Answer

A & E are easy to throw out because of bad comparison. 
Now, B, C and D read equally good. I think I can get rid of 'B' because the use of 'which', in my experience, always refer to the noun immediately before it and comparison need gallons not just water.

C. this underground reservoir contained an estimated quadrillion gallons of water, equal to Lake Huron's , but now reserves are becoming depleted.

D. this underground reservoir contained an estimated quadrillion gallons of water, the equivalent of Lake Huron's, but now reserves are becoming depleted.

Now, relying on my ears, I like the sound of D.

vineetgupta · Answer

D should be the answer.
equal to is only used in the strictest sense eg. 4+3 is equal to 5+2.
Here,equivalent is better.

Himalayan · Answer

i take D.

which in A and b doesnot clealy refer to the quadrilian gallons of water.

briks123 · Answer

I say E.

A and B are wrong because "equal" must be "equals". C is wrong because the water is not actually "equal to Lake Huron's". I'm actually leaning towards E. I think the amount of water is "the equivalent of Lake Huron" literally. What does "Lake Huron's" refer to in D anyway? Lake Huron's water? That doesn't make sense.

ioiio · Answer

I will go with D too.

an estimate can be close to something but wont be equal to something.

rateesquad · Answer

I was split between D and E. But then Huron's......what? It does not specify. So I went with E. I might be wrong although. OA :?:

shoonya · Answer

I think it's B.

I think "which" modifies  gallons of water , not just the  water . Also, equivalent is not right. Now, the question is, whether  equal  satisfied SVA. I think it does. It's the gallons of water, and hence is plural. 

I would love to see more comments on this question. a good one indeed.

anonymousegmat · Answer

i am going with B just because I got a question similar to this wrong today because "equivalent" is a strong word which means more than 'as much as' or something like that.

the use of which correctly modifies water, comparing it to Lake Huron's (water). I could be wrong; I don't know if the apostrophe is enough on the GMAT or if it is too vague and you need a pronoun or something

Since the 1940's the farms and ranches of the Great Plains

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