Shiv2016 wrote:
Construction rule:
Parallelism:
X and Y (no comma unless its a list that includes more than 2 items.)
Why is it D then?
Hey!
Please consider the following correct sentence taken from
OG 15:
There are several ways to build solid walls using just
mud or clay,
but the most extensively used method
has been
to form the mud or clay into bricks, and
,after some preliminary air drying or sun drying,
[u]to lay them in the wall in mud mortar.
As you can see, the two parallel elements in the second clause have been joined by "comma+and". Meaning wise, both these parallel elements
together describe the most extensively used method mentioned in the
but clause. So, if one were to ask you what is the most extensively used method, your answer would be to do x and, post abc (modifier), to do y. So, even when a comma is not a must before the
and joining two elements, it can be used.
Please bear in mind that the comma before the and is NOT part of the modifying phrase "after some preliminary air drying or sun drying". This modifying phrase has its own set of commas, which I have highlighted separately.So, the bottom line is that you cannot consider an answer choice incorrect purely because it joins two elements in a list with "comma+ and" - the complexity of the sentence must be factored in. Adding a punctuation, such as the comma, is the writers prerogative if it aids in a better reading, and therefore, a better understanding of the sentence.
The GMAT is not very likely to give you two identical choices, both of which talk about two elements in a list, convey the same meaning, and are grammatically constructed in the exact same fashion - except that one has a comma before
and , while the other does not.
Cheers!