Hi shobhitk,

The GMAT doesn't test punctuation very often. The exception is that in rare circumstances, a semi-colon might be used (and knowing how/when to use a semicolon is helpful in those scenarios). You'd be better served putting your efforts towards learning the major grammar rules that the GMAT tests, the various idioms that can show up on Test Day and the common patterns that appear in the answer choices.

GMAT assassins aren't born, they're made,
Rich