When it is required to refer to an entire action rather than a single noun, we must use do so rather than do it.

Here the entire action "establish a permanent colony" is required to be referred to , not just "colony". Hence usage of "it" is wrong.

I reject A and E as 'it' as no pronoun referent. We want 'it' to point to the act of building the settlement, but I'm not so sure if 'it' is the correct pronoun to do that.

C and D are out as 'not as Plymouth' does not connect smoothly with 'did' in the non-underlined part of the sentence.

I'll go with B. 'did so' refers to the act of building the settlement and 'but' performs the comparison.

B it is.

I agree with ywilfred on B

I wonder why i marked it as C in my test

I guess you posted it at the same time as I did - to hedge any further contradictions - I agree with anyone who chooses B for this question

It's B.

A) 'it' is trying to replace action of 'establishing colony' (pronoun)
C) & D) both cause problem since 'not' comes directly after 'did'
E) same as 'A'

In fact, this question is of those types where you can judge just by seeing at the first word of the underlined portion.

All choices apart from choice that starts with 'so' is wrong, you need not see the choices for further problems unless there is more than one choice with 'so'.

Any agreements/disagreements?

why cant "it" refer to establishing colony? I feel like you need it or else the sentence does not make sense.

What does "did so" refer to? How are you making the leap that "did so" refers to establishing colony?

In A, 'it' refers to the act of establishing a permanent colony.
However, 'IT' must always refer to a noun, not to an action.
Since in A 'it' refers to an action, it's a wrong sentence.
In B, 'so' correctly refers to establishing a permanent colony.

It is so clearly "B" that I didn't care to read other choices after "B".
which might be very hazardous if I continue doing this

Not sure why 'A' is wrong. Isn't 'it' refers to 'colony' in option A? Any explanation will be really appreciated!!

Thanks Sayantanc2k. Appreciate the help!!

A.it not at Plymouth but
what does it refer to? no referent.

B.so not at Plymouth but
yes "so" is used to present the action. gmat likes the usage of "do so".

C.not at Plymouth but instead
but and instead are redundant. we should use only one contrast word.

D.not at Plymouth but did so
not x but y. here x and y are not parallel.

E.it not at Plymouth but rather
"it" is wrong. not x but rather y is not idiomatic.
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did so...not in..but along. The only option that addresses all necessary parallelism is B.
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This question is based on Idiomatic Usage and Parallelism.

A pronoun can only take a noun as its antecedent. To refer to an action, the adverb ‘so’ is used. On this basis, we can rule out Options A and C.

Option C lacks any reference to the action of settling, so this option can also be eliminated.

Between Options B and D, there is a difference in parallelism of correlative conjunctions. The appropriate pair ‘not-but’ is used in both the options. However, to maintain parallelism of correlative conjunctions, each of the pair of conjunctions must be followed by the same part of speech. For example, if ‘not’ is followed by a noun, so must ‘but’. In Option D, ‘not’ is followed by a preposition (at) and ‘but’ is followed by a verb (did) So, Option D can be ruled out.

Option B maintains the parallelism. In this option ‘not’ is followed by a preposition (at) and ‘but’ is followed by a preposition (along’)
Therefore, B is the most appropriate option.

Jayanthi Kumar.
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