OA : D

I am interested in discussing Option C and Option D.

, a discovery that: what kind of modifier is this?

in C- ,"and it led to to greater understanding of cell differentiation" has pronoun, which creates a reference error with corn
in D:- No such ambiguity .(participial modifier)

richachampion wrote:OA : D

I am interested in discussing Option C and Option D.

, a discovery that: what kind of modifier is this?

In D "a discovery" functions as a summative modifier - a noun phrase that summarizes the idea of a preceding clause. (The clause in this case is "Barbara McClintock discovered a new class of mutant genes.")

Another example, "Dave tore his meniscus, an injury that will keep him off the basketball court for several months." Here, "an injury" is a summative modifier, a noun phrase summarizing the previous clause "Dave tore his meniscus."

In C, "it" has no logical antecedent. Does "it" refer to "class?" Well, that wouldn't make any sense. It was the discovery that led to greater understanding, not the class of mutant genes itself.

richachampion wrote: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
B. a new class of mutant genes in corn were discovered by Barbara McClintock, leading
C. Barbara McClintock discovered a new class of mutant genes, and it led
D. Barbara McClintock discovered a new class of mutant genes, a discovery that led
E. Barbara McClintock, who discovered a new class of mutant genes, leading

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In A and B, the agent of studying seems to be a new class -- the following subject -- implying that A NEW CLASS was STUDYING.
This meaning is nonsensical.
Eliminate A and B.

In C, it seems to refer to a new class -- the only singular non-person noun in the preceding clause -- implying that A NEW CLASS led to greater understanding of cell differentiation.
This meaning is nonsensical:
The intended meaning is that the DISCOVERY of this gene class led to greater understanding.
Eliminate C.

In E, Barbara McClintock (subject) lacks a verb.
The result is an incomplete sentence.
Eliminate E.

The correct answer is D.

OA: While studying the genetic makeup of corn, Barbara McClintock discovered a new class of mutant genes, a discovery that led to greater understanding of cell differentiation.
As David mentions above, the portion in blue is a SUMMATIVE MODIFIER.
The purpose of a summative modifier is to SUM UP the preceding clause.
Conveyed meaning:
The preceding clause in red -- Barbara McClintock discovered a new class -- constitutes a DISCOVERY THAT LED TO GREATER UNDERSTANDING OF CELL DIFFERENTIATION
For another example of a summative modifier, check here:
https://www.beatthegmat.com/abstract-nou ... 74454.html