A teacher asked a student to draw a fish in the sea on a piece of paper.The student drew a fish without the sea.

"Why didn't you draw the sea?"

"The paper would get wet."

An absent-minded professor was lecturing on anatomy. "To show you more clearly what I mean, I have here a parcel with a dissected frog. I want you to examine it very carefully." The professor unwrapped the parcel and saw that it contained two sandwiches and a hardboiled egg. Astonished, the professor said, "I was sure I had eaten my lunch, but where is the frog?"