please resolve cause relation issue >

[great]

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]

[esledge]

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.