I. ABLE - CÓ THỂ

Bob said that the money was not able to be refunded.   ( false )

Bob said that he was unable to refund the money.   ( true )

Bob said that the money could not be refunded.    ( true )

=> Ta chỉ dùng be able / unable to khi chủ từ là người.

II. ADVERTISEMENT - QUẢNG CÁO

On page 4 there is an advertisement about a new computer.    ( false )

On page 4 there is an advertisement for a new computer.     ( true )

=> advertisement for something : quảng cáo cái gì.