As of the presented problem, the most probable answer and the most likely one, out of the options presented together with the problem, would be C. Save As.
Of the menu commands that are there, Save As would serve to be the command that you click when you want to make a copy of a currently open file and rename it. The difference between Save As and Save would be that Save would automatically just replace the old file with the new one, considering that there were changes that took over the file. Save As, on the other hand, would make the old file still available but would prompt the user to choose another file name for it and even presents the possibility of the file being saved in another file extension.