Is it possible to determine from which gun,the bullet was fired,by simly spectating the dead body?(i.e. by seeing the wound on the dead body)

No. A forensics specialist may speculate about the caliber from the wound. But the only way to match to a specific gun is to compare with another bullet fired from the gun.

Yes and no. Scott is correct in a legal and forensic sense so really, his is the correct answer.

If you happened to be dealing with 2 vastly different guns/calibers, it is possible that you could visually tell and make a guess. Say one gun was a .22 LR and one was a .45 ACP... the larger one will cause a more severe wound and it would be obvious which gun that came from. Legally though, the bullets need to be compared to the guns.

You can not tell which specific gun, but as said, you ( may) be able to tell if it was a 22 or a 44 mag. Or a shot gun.

But to say if was that specific gun, youcan not tell from just the body