GMATMadeEasy wrote:The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken apart; rather a kind of nuclear battery that uses natural radioactive decay to produce power.

(A) apart; rather
(B) apart, but rather
(C) apart, but rather that of
(D) apart, but that of
(E) apart; it is that of

OA is B

Q1: option E -> it should refer to "The energy source on Voyager 2" not "nuclear reactor " ? I understand that pronoun ambiguity is not hard and fast rule and that this AC has another error as well .

Would E be correct if written as follows : apart;but it is

Q2: option B -> but rather is considered as correct usage in OG but if we write only "but" instead of "but rather " is it correct too ?

gmat_perfect wrote:

GMATMadeEasy wrote:The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken apart; rather a kind of nuclear battery that uses natural radioactive decay to produce power.

(A) apart; rather
(B) apart, but rather
(C) apart, but rather that of
(D) apart, but that of
(E) apart; it is that of

OA is B

Q1: option E -> it should refer to "The energy source on Voyager 2" not "nuclear reactor " ? I understand that pronoun ambiguity is not hard and fast rule and that this AC has another error as well .

Would E be correct if written as follows : apart;but it is

Q2: option B -> but rather is considered as correct usage in OG but if we write only "but" instead of "but rather " is it correct too ?

Answer to the question No1:

Apart; but it is is not correct for following reasons:

1. Semicolon [;] is used in the following ways in case of two clauses:

1.1. Clause + semicolon [;] + Clause

Example:
They were playing cricket; I was playing football.
--> Two clause has been joined by semicolon, and every clause MUST have a subject and a verb.

1.2. Clause + Semicolon [;] + Conjunctive Adverb + COMMA + Clause

They were playing cricket; however, I was playing football.

Mind: All the clauses are independent clause.

In your example, Semicolon [;] + But it is, the clause after semicolon is not independent clause. It is coordinating clause.
You cannot join coordinating clause with semicolon. You need just a comma before coordinating clause.

Example:

I was plating for a long time, but I could make good number of runs.

Answer to the question NO. 2:

Nope, it is not correct to use "COMMA + BUT + dependent clause"

Mind the following two things:

2.1. "COMMA + BUT" needs an independent clause after it if "comma + but" is not used in a list of NOUN or in case of "not only X, but Y" construction.
2.2. "COMMA + But rather" needs a NOUN after it.

Another issue:

See the example:

The source of light is not the moon, but the sun.
--> We should not use "that of" because "that" does not have reference.

The light of moon is less bright than that of the sun.
--> We need that because "that" has reference, the light.

We can write the sentence as "the light of the moon is less bright than the light of the sun".

Thanks.

2.1. "COMMA + BUT" needs an independent clause after it if "comma + but" is not used in a list of NOUNor in case of "not only X, but Y" construction.

GMATMadeEasy wrote:gmat-perfect , that is just perfect.

2.1. "COMMA + BUT" needs an independent clause after it if "comma + but" is not used in a list of NOUNor in case of "not only X, but Y" construction.

Could you clarify the bolded part in abpve qoute ?

GMATMadeEasy wrote:The energy source on Voyager 2 is not a nuclear reactor, in which atoms are actively broken apart; rather a kind of nuclear battery that uses natural radioactive decay to produce power.

(A) apart; rather
(B) apart, but rather
(C) apart, but rather that of
(D) apart, but that of
(E) apart; it is that of

OA is B

Q1: option E -> it should refer to "The energy source on Voyager 2" not "nuclear reactor " ? I understand that pronoun ambiguity is not hard and fast rule and that this AC has another error as well .

Would E be correct if written as follows : apart;but it is

Q2: option B -> but rather is considered as correct usage in OG but if we write only "but" instead of "but rather " is it correct too ?