SC is a tricky question type. Many students tend to rely on the way in which an answer choice sounds, thereby effectively turning off their grammar brain. Turning on the grammar brain, while tough going at first, will reap rewards in the long run. Not only will you understand the grammatical rules behind each sentence, but you will become faster at spotting the errors in the wrong answer types (which will make you a lot faster!).
The tough going I mentioned earlier requires that you know your grammar fundamentals. Manhattan GMAT
's guide is excellent in this regard. I've used it with many of my tutees, and even before they are half way done with the book they are speaking in grammar-ese
. For video learning, Magoosh
offers helpful videos that will also help you become adept at the fundamentals.
Once you get the hang of the grammar rules, becoming faster is a matter of doing practice questions and learning to spot the more obvious errors (S-V agreement, Misplaced Modifiers, etc.) Of course do not speed up too soon. Take your time in the beginning, otherwise you'll very likely switch back to relying on your ear (which is especially likely to happen in the tense-fraught environment of the actual GMAT).
Good luck, and let me know if you have any other questions
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