keerok
No.
Nikkor C series lenses came with the Nikon S-mount which was used with early Nikon 35mm rangefinders. It was almost similar and somewhat compatible to the Contax mount.
The D40 uses an F-mount which is not compatible to the S-mount. No, you can not mount the Nikkor C directly to a D40. Since the distance from the lens flange to sensor/film is much longer on the F-mount than the S-mount, it would be close to impossible finding an adapter that will allow using a Nikkor S-mount lens on a Nikon F-mount body.
?
No. The Nikkor-C lenses were designed only for Nikon's rangefinder camera. The Nikkor-C lenses have a different mount are too small to fit onto the Nikon F mount.