A gentleman travelling in a railway carriage was endeavouring, with
considerable earnestness, to impress some argument upon a
fellow-traveller who was seated opposite to him, and who appeared rather
dull of apprehension. At length, being slightly irritated, he exclaimed
in a louder tone, “Why, sir, it’s as plain as A.B.C.” “That may be,”
quietly replied the other, “but I am D.E.F.”