【明報專訊】Snails , crabs, clams and things like that with very soft bodies live in hard shells for protection. Sometimes people do, too. If they are shy, timid, withdrawn - or even afraid - they are said to live in a shell. "Sidney used to be a happy and active fellow, but today he lives in a shell and doesn't seem to have any friends." "Dion is very active and has many, many friends. No one would say she lives in a shell!"