A concave mirror of focal length f forms an image of the moon. Where is the image located?

A、Atthemirror’ssurface.;
B、Almostexactlyadistancefbehindthemirror.;
C、Almostexactlyadistancefinfrontofthemirror.;
D、Atadistancebehindthemirrorequaltothedistanceofthemooninfrontofthemirror.