anmolio wrote:
GMATNinja, Please help with this, how to tackle the use of "-" in a sentence.
Here's the thing about dashes: they can do basically anything. They can separate independent clauses. They can be used to set off modifiers. They can be used to introduce examples. So when you're looking at a dash (or dashes) in an SC problem, it's not helpful to think about iron-clad rules. Instead, just consider the context.
In this case, we get a descriptive clause set off by dashes: "—they are often green and striped, or have plenty of bumps and bruises—" It appears to be providing additional information about the preceding clause, telling us
how heirloom tomatoes are less appetizing than their healthier-looking relatives. And because it seems to be setting off a non-essential modifier in the same that, say, commas might set off a modifier, its role in the sentence doesn't appear to be vital.
So if I saw this on the exam, I'd spend very little time worrying about it. It's in the non-underlined portion, and aside from providing a bit of background, doesn't really impact the rest of the sentence.
The takeaway: you don't need to know tons of esoteric grammar or punctuation rules for SC! You can usually figure out what's going on by using a bit of context and logic. And anytime a rule is fuzzy, or you're not sure if there is one, you'll want to move on to other elements of the sentence.
For more on GMAT punctuation -- including a fairly long rant about why you shouldn't really worry about dashes -- check out
this video.
I hope that helps!