Hi Khurram,
Thanks for the detailed response. I came across this question in PM Fastrack. The explanation simply states that all remaining risks that you have decided not to do something about must be documented and revisited later. After reading your response and the PMBOK4 guide, here is what I have come to understand:
After Plan Risk Response, you are left with residual risks i.e. known unknowns. Contingency plans may be developed for SOME of these residual risks (aka active acceptance), while the rest may be dealt with as and when they occur (aka passive acceptance). However, ALL residual risks must be documented as such in the risk register and revisited later during Monitoring & Controlling. Keeping this in mind option (A) is definitely true, but option (

may or may not be true. Hence, I think PM Fastrack may be correct.
Going back to my original question, I had also asked you what is a Contingency Reserve. If I understand correctly, Contingency Reserve is a type of Contingency Plan i.e. it is a time or cost reserve set aside for known risks that the management has decided to accept. Page 304 of the PMBOK4 guide confirms this: "The most common active acceptance strategy is to establish a contingency reserve, including amounts of time, money, or resources to handle the risks."
On the other hand, a Management Reserve is purely meant for unknown unknowns. The differences between all these terms are very subtle and tricky!
Please correct me if I am wrong.