(A)
The Standard & Poor's 500 fell as much as 8 percent during the five weeks following the 2000 election between George W. Bush and Al Gore. - No issues in this option. The sentence is well structured with its meaning kept crystal clear. Hence keep it.
(B) The Standard & Poor's 500, during the five weeks following the 2000 election, fell
as much as 8 percent between George W. Bush and Al Gore.- The highlightened part is wrong and renders an obscure meaning.
(C) During the five weeks following the 2000 election, the Standard & Poor's 500 fell
as much as 8 percent between George W. Bush and Al Gore.- Again wrong . It has the same problem that the second option has.
(D) The Standard & Poor's 500 fell
as much, during the five weeks following the 2000 election between George W. Bush and Al Gore,
as 8 percent. - The "as much as" is a single intact unit and should be used without getting interfered by any other dependent clause.
(E) Following the 2000 election between George W. Bush and Al Gore, the Standard & Poor's 500 fell as much as 8 percent
after five weeks. - Trap. Looks kinda fine at first but "After" makes it ambiguous. It would have been better if "during" was used instead of "after" .
A is the only one without any error , THUS A .