GMAT Sentence Correction (SC) | Re: Recently implemented

The comma before "And" does not necessarily suggest that the last item in the parrallel list be "Independent clause"

AND - is used to join entities

X, & Y - If X is IC then Y needs to be IC to maintain parallelism.

In this case, X,Y, Z, & A - The last element is not parallel with the remaining 3 elements. The last element is out of sync. So, it needs to be removed.

The correct option (C) - does the same. X - Have