For me, Sentence Correction is a bit of a detective game. You need to know if something's wrong, and then if you decide this is the case, you need to find out where it is wrong, and be clear about why it is wrong.

And if you decide that's it's fine after all, you need to be clear about why this is the case!

That's the GMAT all over - can you get to the point? Do you know what you know, and what you don't know? It's not about gut feel! Very forensic. CSI, you might say. Correct Sentence Investigation. [Cue rock guitars, red haired investigators with husky accents, Shatner-like voice inflections and an uncanny ability to get to the right answer. Me, basically.]

So, here is a mantra I follow when attacking a Sentence Correction problem. Repeat it to your benefit, avoid it at your peril...

Remove Distracting Text

What text is NOT part of the problem?

Have a look at the following simple example:

Since 2005, the number of sports cars on the roads have grown from 4 million to nearly 12 million.

a) have grown from 4 million to nearly 12 million
b) grow from 4 million to nearly 12 million
c) grew from 4 million to nearly 12 million
d) grows from 4 million to nearly 12 million
e) has grown from 4 million to nearly 12 million

While this is still a fairly small problem to analyse, there's no point in analysing any more evidence of alleged grammatical wrongdoing than we need to! So, let's slip on the shades, hop out of the Ferrari, and sift through the evidence.

What's DEFINITELY not part of the problem? If we can make the text area for analysis smaller, then we will stress out less by knowing that we're not going down an investigative dead end. And while those dashing American crime fighters have a whole 50 minutes per episode to find out whodunnit, we have less than 2 minutes. i.e. our life is a whole lot tougher.

What do we notice about the 5 different options? Anything strike you about them? Well, I keep seeing this line about from 4 million to nearly 12 million. in fact, they are ALL saying the same thing!

So, if all 5 options agree on something, then YOU KNOW something else, which is the repeated text is NOT PART OF THE PROBLEM. So, mentally, strike it out of the options AND the underlined text.

(Huskily) Sergeant, remove this street rat from the list of suspects. (Peer over shades) But don't think I won't be back... Someday...

Thank you.

Now, what do we have left? Our sentence really looks like

Since 2005, the number of sports cars on the roads have grown ....

a) have grown ...
b) grow ...
c) grew ...
d) grows ...
e) has grown ...

And now, we apply the rules [Hint : try subject verb agreement, and tense. And for tense, draw a timeline to be really sure of which tense you should be using]

And when you select the right option (hint : there IS an offender here) where do you send 'em? That's right! The State Sentence Correctional Facility.