On every verbal question, there is 1 right answer and 4 wrong answers. No such thing as a less good right answer.

On Reading Comprehension, difficult wrong answers are often wrong because just one word in that choice does not match the information in the passage.

On Sentence Correction, clarity and meaning are important considerations. There are many choices that, while grammatically correct, either do not have the correct meaning or are not clearly written. One example of difference of meaning can be as subtle as the difference between "first aired on evening radio in the 1920's" and "aired first on evening radio in the 1920's." When two choices express different meanings, it's important to choose the answer choice that best matches the meaning of the original sentence.

I hope this information helps. Good luck in your studies!

Thank you David for your reply.
That's what I thought indeed as I actually felt for that trap many times the first time I passed the GMAT (more than one answer that seemed correct to me...)
I am planning to work intensely on that area. Thank you again for your advise, indeed one has to pay attention to every little detail in order to catch the correct answer.

Sorry, just 1 right answer per question.