This is not a GMAT-study-specific answer (we are definitely not GMATSnark!) but here's where we see it not working:

If you take it apart, the second bit can be rephrased as "The reasons behind last week's rally were..."

You can't substitute "they" in that sentence: "They behind last week's rally were..."

We can't offer any insightful commentary or explanation as to why not, so hopefully some of the real experts will chime in - but doing that substitution seems to show that E is wrong.

(PS: You might want to use the spoiler tag on your discussion of right/wrong answers too - it sorta defeats the purpose of spoilers if you're gonna lay out which one is good immediately after. )

Hi essaysnark ,

Thanks for the suggestion. I have used spoiler for the explanation part as well. its still not clear why E is wrong

FOR E, the sentence looks like :

The reasons for yesterday's sharp rise in the stock market were much the same as they were behind last week's rally: a surge in the economy to a 5.6 percent annual growth rate and improved corporate earnings balanced by the lack of signs of inflationary pressure.

Substituting pronoun

The reasons for yesterday's sharp rise in the stock market were much the same as reasons were behind last week's rally: a surge in the economy to a 5.6 percent annual growth rate and improved corporate earnings balanced by the lack of signs of inflationary pressure.

I still can't make out whats wrong with choice E