Consider the list of page references in the time line as below:
9 6 2 3 4 4 4 4 3 4 4 2 5 8 6 8 5 5 3 2 3 3 9 6 2 7
What is the working set at the penultimate page reference if $$\triangle$$ is 5?

A

{8, 5, 3, 2, 9, 6}

B

{4, 3, 6, 2, 5}

C

{3, 9, 6, 2, 7}

D

{3, 9, 6, 2}