While studying the genetic makeup of corn, a new class of mutant genes

who "studying" here is Barbara, not the " new class of mutant" . Thus, eliminate A and B.
What " leading" here is the discovery , not Barbara. Eliminate E.
"it" in C has no ante-decent, thus C is out.
I'm left with D.

A. misplaced modifier
B. misplaced modifier
C. 'it' doesn't have a clear noun that it can refer to.
D. Best choice. Clear and concise.
E. awkward

This is a simple question and you can answer it correctly by just figuring out the correct structure you can get among the answer choices.
First, analyze its building blocks in clauses and then know what each element is.

Correct answer choice D looks like this:

Subordinate Clause + Main Clause + Subordinate Clause

Opening Modifier + Subject, Verb, Object + Noun+Noun Modifier (modifying preceding clause)



Hope it helps

This sentence opens with a modifying phrase. It's very useful to notice sentences that open with such phrases because as soon as we recognize this common GMAT pattern, we know that whatever follows the comma must be the thing the modifying phrase is modifying.

Here, the phrase "While studying the genetic makeup of corn" is modifying whoever was doing the studying. That means that the person conducting the study (the thing to which the modifying phrase refers) must follow the comma.

So Barbara McClintock should follow the comma. A and B are gone.

In C we can assess the pronoun it. To assess a pronoun we need to make sure that 1) the pronoun refers to the intended 'antecedent' (the thing the pronoun is filling in for), 2) the pronoun agrees in number with its antecedent and 3) there are not other potential antecedents the pronoun might refer to.

Here, the it in C grammatically refers to 'a new class', the only singular noun-phrase available to us. But the intention of the sentence is to say that the discovery led to a greater understanding, not that the new class itself let to a greater understanding.

So C, by using a pronoun with an unintended antecedent, changes the meaning of the sentence.

We can get rid of E by noticing that the sentence is incomplete without an active verb attached to the subject. The sentence, with E, never tells us what Barbara McClintock did.

While studying the genetic makeup of corn, a new class of mutant genes was discovered by Barbara McClintock, a discovery which led to greater understanding of cell differentiation.

A. a new class of mutant genes was discovered by Barbara McClintock, a discovery which led - modifier issue
B. a new class of mutant genes in corn were discovered by Barbara McClintock, leading - modifier issue
C. Barbara McClintock discovered a new class of mutant genes, and it led - pronoun it antecedent issue
D. Barbara McClintock discovered a new class of mutant genes, a discovery that led - Correct
E. Barbara McClintock, who discovered a new class of mutant genes, leading - no main verb

Answer D
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in the option d, i believe that there is run on error as two sentences " mutant genes, discovery that led " are two complete clauses which are connected with comma, expert advice if any

Hi mohitmonika123,

"A discovery that led to greater understanding of cell differentiation" is not a clause. It is a noun phrase.

a discovery that led to greater understanding of cell differentiation

The that led... bit is a clause, but it is just a modifier for the noun discovery.
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Explanation:

A. Eliminate.
The modifier 'While studying the …’ incorrectly modifies 'a new class of genes'. It should rather modify Barbara M. "which" must be separated by commas.

B. Eliminate.
The modifier 'While studying the …’ incorrectly modifies a new class of genes'. Same as Option A. Singular 'class of genes' needs singular 'was', not plural 'were'.

C. Eliminate.
The antecedent of 'it' is not very clear.

D. Correct Answer.
The absolute modifier is correctly used. Modifiers are correctly placed and structured.

E. Eliminate.
If the modifiers are removed the sentence reduces to 'While studying the genetic makeup of corn, Barbara M, leading to ...'. This is a sentence fragment as there is no active verb.

Hope this helps!
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The two concepts tested here are Modifiers and Tenses.

Option A – The modifier ‘while studying…’ incorrectly modifies ‘a new class of genes’. It should rather modify Barbara. ‘Which’ must be separated by commas. Eliminate.

Option B – Same as A. A case of incorrect modification. Singular 'class of genes' needs singular 'was', not plural 'were'. Eliminate.

Option C – Pronoun ambiguity. The antecedent of 'it' is not very clear. Eliminate.

Option D – Correct Answer. The absolute modifier is correctly used. Modifiers are correctly placed and structured.

Option E - If the modifiers are removed the sentence reduces to 'While studying corn, BM, leading to ..'. This is a sentence fragment as there is no active verb.Eliminate.

Hope this helps!
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While studying the genetic makeup of corn, a new class of mutant genes was discovered by Barbara McClintock, a discovery which led to greater understanding of cell differentiation.

A. a new class of mutant genes was discovered by Barbara McClintock, a discovery which led
Modifier issue

B. a new class of mutant genes in corn were discovered by Barbara McClintock, leading
Modifier issues at both end

C. Barbara McClintock discovered a new class of mutant genes, and it led
pronoun issue

D. Barbara McClintock discovered a new class of mutant genes, a discovery that led
No remarks

E. Barbara McClintock, who discovered a new class of mutant genes, leading
verb issue, S-V pair missing

IMO D
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