You are upgrading your Cisco router IOS from a TFTP server over the network. The upgrade procedure is stopped and you are prompted to erase the current flash contents before continuing. What is most plausible reason for this? （）

A. There is insufficient room for more than one image.
B. The router has detected a copy of the current software image on the TFTP server.
C. The file can be relocated and not compressed.
D. The image to load is a binary executable file.