Retailers reported moderate gains in their November sales, as much bec

This is a question based mostly on parallelism of comparison.
The comparative expression is in the form of the correlative conjunctions - ‘as----as’.

The options also give us the choice between the expressions “because of” and “because”.
The difference between them is that “because of” is followed by a noun or noun phrase and “because” is followed by a clause since it acts as a subordinating conjunction.

In Option A, the expression “because of” is followed by a noun + participle phrase - “their sales of a year earlier being so bad”. This construction is not considered stylistically graceful. So, Option A can be eliminated.

In Option B, the use of an extra ‘as’ changes the meaning and distorts the comparison.
“as much because of their sales a year earlier having been as bad as because”
The second highlighted portion implies a comparison leaving the first highlighted comparative expression incomplete. So, Option B can be eliminated.

In Option C, the errors of Options A and B have been repeated. So, Option C can also be eliminated.

In Option E also, there is an extra comparative word ‘as’, leaving the comparison incomplete. So, Option E can also be eliminated.

In Option D, the comparison is complete –
“as much because their sales a year earlier had been so bad as because shoppers were getting a head start on buying their holiday gifts”

The rule of parallelism of correlative conjunctions states that whatever kind of word (noun, verb, preposition etc.) comes after the first of the pair of conjunctions must also be present after the second of the pair of conjunctions.
So, the parallelism has also been maintained in Option D – the conjunction 'because' is present after each of the pair of conjunctions.
“as much because their sales a year earlier had been so bad as because shoppers were getting a head start on buying their holiday gifts”
Therefore, D is the most appropriate option.

Jayanthi Kumar.