Is a single witness testimony sufficient to prove any fact?

Generally, the testimony of a single witness is sufficient to prove any fact. (See People v. Barnwell (2007) 41 Cal.4th 1038, 1052.) " 'To warrant the rejection by a reviewing court of statements given by a witness who has been believed by a trial court, there must exist either a physical impossibility that they are true, or it must be such as to shock the moral sense of the court; it must be inherently improbable and such inherent improbability must plainly appear." ' (People v. Jones (1970) 10 Cal.App.3d 237, 247.)