Of inalienable nouns.
Run it through a native speaker and stop embarrassing yourself. This course is riddled with mistakes like these and I’m sick and tired of having my answers disqualified because you’ve kept these mistakes in place months after its release.
The senrtnce is wierd to begin with but without further context the usual assumption would be that the leg is his own, in which case we do not say "the leg". Now, if we are talking about a chicken leg, a frog leg, or some other dismembered ambulatory extremity, we might say "the leg" provided it is clear to both sides of the conversation just what we are talking about.
Again, if there is something about the subject that merits distinguishing one of his legs from the other, e. g., one leg is broken, then we might say "the leg" once it is perfectly clear which leg is being referenced. We do not say "the leg" unless the reference is clear and specific.