Boy was milking his cow

Asmall farm boy was milking his cow when all of a sudden a bull came
charging towards him. As horrified workers nearby watched, the boy calmly
continued his milking.
To everyone?s astonishment, the bull stopped a few inches from the boy,
turned around and walked away . ?Weren?t you afraid?? one of the workers
asked the boy.
?Not at all,? the boy replied , ?I knew this cow was his mother-in-law.?