At a class of Rangers training the instructor told the students: "A good Ranger is always attentive to everything around him - people and animals. He should be able to identify animals by sound and even determine how many of them are there in an area. Now let's have an exercise. I'll hide in those bushes and give you a sound. Listen!"
In the bushes he imitated, rather skillfully, the braying of a donkey three times. Then he asked: "So how many and what animals were there in the bushes?"
"One ass," was the unanimous reply.