Answer
$495$ different sets of questions.
Work Step by Step
1) It is not a sequence of choices.
2) The order in which the questions are answered does not matter.
Combination of 12 distinct questions taken 8 at a time:
$_{12}C_8=\frac{12!}{8!(12-8)!}=\frac{12!}{8!\times4!}$
But, $12!=12\times11\times10\times9\times(8\times7\times6\times5\times4\times3\times2\times1)=12\times11\times10\times9\times8!$
$_{12}C_8=\frac{12\times11\times10\times9\times8!}{8!\times4!}=\frac{12\times11\times10\times9}{4\times3\times2\times1}=\frac{11880}{24}=495$
