Hi Sri,

"which" should technically be used to introduce information that concerns every object of the type described. Conversely, "that" should be used to introduce information about the individual object described, not every object of the type.

(1) The Panda bear, which is not really a bear, has been on the brink of extinction for decades.
(2) The Panda bear that we saw at the zoo the other day has been moved back to its native China.

In (1), "which is not really a bear" doesn't describe an individual bear but every object of the Panda bear type. In (2), "that we saw at the zoo" refers to an individual bear.

(3) Infectious diseases, which are responsible for 2 out of 3 deaths among children, would be a lot less dangerous if we had better preventative care.
(4) The infectious diseases that cause most children's deaths would be a lot less dangerous if we had better preventative care.

In this sentence, "which are responsible for children's deaths" does not refer to an individual disease, but to every object of the infectious diseases type. In (4), "that cause children's deaths" refers to a specific set of diseases, not to all infectious diseases.

Going back to your sentence:

The earthquake that destroyed Lisbon in 1755 is famous > The earthquake, which destroyed Lisbon in 1755, is famous. This is because "that destroyed Lisbon" describes an individual earthquake, not all earthquakes.

-Patrick

gmattesttaker2 wrote:Hello,

Hello,

This is from MGMAT SC Guide P. 93. I was wondering if you can please tell me why my answer is in-correct. Thank you very much.


For each of these modifiers, (1) identify the word or words, if any, that it modifies, and (2) indicate whether the modifier is correct. If the modifier is incorrect, suggest a way to correct the error


9) Of all the earthquakes in European history, the earthquake, which destroyed Lisbon in 1755, is perhaps the most famous.

My answer:
Of all the earthquakes in European history, the earthquake which destroyed Lisbon in 1755 is perhaps the most famous.

Book answer:
[spoiler]Of all the earthquakes in European history, the earthquake that destroyed Lisbon in 1755 is perhaps the most famous.[/spoiler]
I thought in this-case "which" was referring to "earthquake"


I was just wondering if you can please assist here. Thanks a lot.

Best Regards,
Sri

Which serves to introduce a NON-ESSENTIAL modifier.
A NON-ESSENTIAL modifier can be removed without changing the basic meaning of the sentence.
If we remove the which modifier from your sentence, we get:
Of all the earthquakes in European history, the earthquake is perhaps the most famous.
This sentence makes no sense.
The modifier that was removed is ESSENTIAL to the meaning of the sentence.
To introduce an ESSENTIAL modifier, we use that:
Of all the earthquakes in European history, the earthquake THAT destroyed Lisbon in 1755 is perhaps the most famous.