A is wrong because "a discovery" is referring to "Barbara" which is incorrect.
B --> "were" is incorrect for singular "a new class"
C --> "it" is ambiguous. It raises a question whether genes led to... or the discovery led to...
D --> This clearly specifies that it was discovery that led.
E --> Usage of commas is not justified. It confuses what is leading. Is it Barbara or discovery.
One more point to note in this question.
In the initial sentence "a new class" is coming after comma, suggesting that mutant genes was studying genetic makeup

Thank you. make sense now.

A = while studying...person shd follow.
B = same as A.
C = it has no referent.
D = correct
E = leading is incorrectly used.

Answer D
but i have a doubt here
if it has which instead of that in the D option.
is it correct.
as which should refer to a noun, i have a doubt like whether the which is referring to the word discovery or the the entire clause a barabara mcclintock discovered a new class of mutnat genes.

please some body clarify

thanks:)

nanda323 wrote:Answer D
but i have a doubt here
if it has which instead of that in the D option.
is it correct.
as which should refer to a noun, i have a doubt like whether the which is referring to the word discovery or the the entire clause a barabara mcclintock discovered a new class of mutnat genes.

please some body clarify

thanks:)

Hi Nanda,

IMO

No it would be wrong... You can remember the same simply as follows......quite mechanical

"which" without comma (when used as relative pronoun) is always wrong in GMAT. i.e. "blah blah is a discovery which...." is Wrong in GMAT.

that with comma is always wrong in GMAT. i.e. "blah blah, discovery that...." is Wrong in GMAT.

There is a grammatical reason for the same that is pretty well explained in Manhattan SC guide.