Option A. Over lays
Because, In over lay scheme, programmer has to worry about the memory mgmt. In RTOS, the memory mgmt has to be done statically. Hence Overlays.
Why not pipeline?
//update here
Why not Swapping ?
Because objective of real time OS is to give results with in seconds. for example, missile control system. And we know that getting data from HDD has delay involved in it. Hence Swapping is not used.
ThatsIt