One day, a class of third graders from the city were taking a field trip
to the country to visit a small farm. The kids were amazed to see all
the different kinds of animals on the farm.

The farmer asks one little girl,
"What's the difference between a rooster and a hen?"

"The hen lays eggs," replied the little girl.

"Very good!" said the farmer. Then he asked another little girl, "What's
the difference between a duck and a turkey?"

"Well," replied the little girl. "Turkeys can't swim and turkeys are
what we have on Thanksgiving Day."

"Very good!" exclaimed the farmer. Then he asks Little Johnny,
"Do you know the difference between a bull and a cow?"

"Yes, I do," replied Little Johnny, "Bulls smile when you milk them."