Augustus DeMorgan made many valuable contributions to

I chose A for the following reasons:
1. the Qn has non-essential modifier marked with ",". Thus we can disregard it. Subject contribution, verb is known as contribution is singular. Options A and D left;
2. Verb define in option D changes the meaning the sentence - we don't know for sure, whether they defined or concerned complementation of sets. Option A left.

I am confused with choosing A or D. It helps me answer my question.
Thank your for exp.
+1 kudos

Augustus DeMorgan made many valuable contributions to calculus, trigonometry, algebra, and logic; but perhaps his most famous academic contribution, a pair of theorems concerning complementation of sets, is still known today as DeMorgan’s Rules.

his most famous academic contribution-------> Contribution referes to Singular Object...

So the decision point is IS / ARE

The correct answer will include IS , Only OPtions (A) and (D) are available...

(D) two theorems that define complementation of sets, is ----> Two theorems............must be are

(A) a pair of theorems concerning complementation of sets, is -----> A pair of ........ is (Correct)


Hence (A) is the best choice...

Subject-verb combination quickly eliminated B, C and E due to plural verb are.

Coming to A and D, both are different in meaning.



a pair of theorems related to complementation of sets is not the same as two theorems that define complementation of sets since we do not know whether theorems are just related to the complementation of sets or they define complementation of sets.
We cannot assume so go for A.

subject ‘contribution’ plays a key role in deciding the answer here. First being a singular subject, the subject’s verb also should be singular –i.e.: is, dismissing B, C and E.

answer A .

The subject w/r/t the state of being verb (is/are) is "academic contribution" - this is singular
The modifier that comes after simply describes the contribution but does not change its person (singular/ plural)

A

1st split contribution is/are - should be singular = B,C,E - out
2nd split a pair/ theorems - contribution is singular so, the modifier should be also singular = D - out

The answer is A

Augustus DeMorgan made many valuable contributions to calculus, trigonometry, algebra, and logic; but perhaps his most famous academic contribution, a pair of theorems concerning complementation of sets, is still known today as DeMorgan’s Rules.

a.a pair of theorems concerning complementation of sets, is

b.a pair of theorems concerning complementation of sets, are

c.two theorems that have to do with complementation of sets, are

d.two theorems that define complementation of sets, is

e.two theorems that are both related to complementation of sets, are

Dear Experts,
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I rejected 'option d' on the basis that 'two theorems that define complementation of sets' is an independent clause that is modifying 'academic contribution.' We need a modifier rather than an independent clause. Thus selected option A.

Let me know if this is the right approach/knowledge applied?


-Romil

Romil, "two theorems that define complementation of sets" is not an independent clause; it's a noun phrase composed of a noun, "theorems," and modifiers that modify "theorems," "two" and "that define complementation of sets." So, "two theorems that define complementation of sets" could certainly serve as an appositive that modifies "academic contribution."

The only valid reason to eliminate (D) is that "two theorems that define complementation of sets" is a plural subject and, thus, does not agree with the singular verb "is" that follows it. That said, since the singular "contribution" rather than "two theorems" is the subject of "is," one could argue that the version of the sentence created via the use of (D) is not clearly incorrect, though the version created via the use of (A) does seem to be the best one since the singular "a pair" works nicely with both "contribution" and "is."

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