Which of the following statements related to Bus are correct?
Option A: A bus, in the sense, is a common collection of signal pathways over which related devices communicate within the computer system.
Option B: Expansion buses such as PCI and AGP allow the insertion of external devices, or adapters, into the bus.
Option C: Buses exist within the system to allow communication between the CPU and components with which data must be exchanged.
Option D: All of the above.