Placement of comma

{A} - Incorrect: it's an run on sentence.
{B} - Incorrect: we need "and"
{C}
{D} - Incorrect: we need "and"
{E} - Incorrect: the part after semicolon is not clause.

{C}???

Hey shibsriz,
This sentence features a couple of issues; let’s spot and take care of them.

A) Good example of the so called “run-on” sentence. A “run-on” sentence has two independent clauses; it is a structural flaw that is fixed with the introduction of a subordinator to properly connect the two sentences. In particular, when two independent clauses are connected only by a comma the ensuing “run-on” structure is called “comma-splice”.
B) Same error here. We need a conjunction to connect those clauses.
C) Comma-splice issue has been fixed, moreover there’s a neat parallelism. Correct.
D) The word “now” is in the wrong place and conveys a skewed meaning. Comma-splice error.
E) The use of semi-colon corrects our comma-splice issue, but what should follow the semi-colon is a full clause not a fragment. Thus this one is incorrect.

Hope it helps,
-tathastuGMAT