The relationship between cell phone use and the incidence of brain tumors is still unclear, this is because some studies show a causal relationship while others do not.
a) is still unclear, this is because some studies show
b) is still unclear; some studies show
c) are still unclear because some studies show
d) is still unclear because: some studies show
E) is still unclear; the reason is that some studies show


source : Manhattan online tests

Answer : b
==================explanation by manahattan ===========
The original sentence incorrectly uses a comma to join two independent clauses. As is the case with the two clauses in this sentence (“The relationship…is still unclear” and “this is because some studies show…while others do not”), independent clauses contain a subject and a verb and can stand alone as independent sentences. While semicolons can join two independent clauses, commas cannot. Further, “this is because” is unnecessarily wordy.

(A) This choice is incorrect as it repeats the original sentence.

(B) CORRECT. The semicolon correctly connects two independent clauses. Also, the singular verb “is” agrees in number with the singular subject “relationship.”

(C) The plural verb “are” does not agree in number with the singular subject “relationship.”

(D) While “is” agrees in number with the singular subject “relationship,” the colon is used incorrectly in this choice. Colons must be preceded by independent clauses. Independent clauses contain a subject and a verb and can stand alone as independent sentences. In this case, however, the colon is preceded by “The relationship…is still unclear because,” which is not a clause that can stand alone as an independent sentence.

(E) While the semicolon correctly connects two independent clauses, and while “is” agrees in number with the singular subject “relationship,” “the reason is that” is unnecessarily wordy. The more concise version in answer choice (B) is preferred.
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doubt

What we are having is a cause and effect thing .
The relationship between cell phone use and the incidence of brain tumors is still unclear, this is because some studies show a causal relationship while others do not[b]

effect occured ... because ..cause ...

Since answer choices do not take care of this (except a & e of which E is too bad) should i not select A because meaning should not change in any case ..

I am unclear on this . please tell me what have i missed here and how to tackle these types of situation in GMAT .[/b]

I think you are overthinking the meaning, and not focusing enough on the grammar and the answer choice splits (especially punctuation).

The background situation (cell phone use/brain tumors) may be cause and effect, but there is no "because" between those two things. In this sentence, we have two grammatically independent clauses that are related in meaning: 1) The relationship is unclear, and 2) some studies show a relationship but others do not. The semicolon is required in such a structure.

(A) is wrong because a comma between independent clauses (i.e. clauses with a verb) creates a run-on sentence.

_________________
Emily Sledge
Instructor
ManhattanGMAT