Sentence Correction

bjp2008 wrote:

dumb.doofus wrote:

ankit1383 wrote:Is those refering to light ???
sources cannot be fainter....only light can...
is light plural ???
Still cant ifgure out why those is used in the OA

"Those" is referring to sources buddy..

answer this: What can be detected by ground based instruments?
Sources . isnt it??

Well, any instrument ground based or space based captures light emitted by these sources to detect them..

Let's break the sentence to make it clear to you..

1. The Hubble Space Telescope will capture light from x
2. x is twenty times fainter than y
3. y can be detected by ground-based instruments.

As you can see we are comparing x and y.. so both have to be same.. and they are sources..

hope this helps..

How could the sources be fainter??? It is the "Light from Sources" is fainter. I think its C. The Hubble Space Telescope will capture [light from x] twenty times fainter than [light from Y] can be detected by ground-based instruments. Please clarify..

Good questions -- found this great explanation on another site:
We are not sure whether the comparision is for "light" or for "sources". So the choice could be either C or D.

Now, let us examine C

C has used "that". So logically "that" is referring singular noun-"light". If we replace "that" with "light", the sentence becomes

The Hubble Space Telescope will capture light .....twenty times fainter than light can be detected by ground-based instruments.

This sentence is awkward.
We need some construction similar to

The Hubble Space Telescope will capture light .....twenty times fainter than that [light] which can be detected by ground-based instruments.

Now, let us see D,
D uses plural "those". So logically "those" is referring plural noun-"sources".

The Hubble Space Telescope will capture light from sources twenty times fainter than those [sources] that can be detected by ground-based instruments.

This sentence is OK. So D should be answer.

https://www.urch.com/forums/gmat-sentenc ... those.html

any one please, explain why answer choice A is wrong.
for those who are basing their explanation on idiom "compared to" and "compared with"
please visit link: https://www.manhattangmat.com/forums/whe ... t2071.html
it is clearly mentioned that answer choices can not be eliminated merely because of idiom "compared with" and "compared to" .. many thanks.

IMO D