The Empire State Building holds about 900 tenants for business, but most of them are ______.

A．He has edited three books.
B．He has bought the wrong book.
C．He has lost half of his money.
D．He has found the book that will be used.

A．Three types of noise that can make communication difficult.
B．The meaning of external noise.
C．The effect of cigarette smoke.
D．The reason why you can become speechless.