In manufacturing, cheaper materials are constantly being        for the better, more expensive kind.

 ------The school is well equipped.------Yes, and every student has free ________to the library.

 ---The light was on all night long. ---Yes. It seemed that Mike ________. He was the last one to leave the office.

He didn’t ________ what I read because his mind was on something else.

Most students think this book is useful as it ____ all the basic grammar rules they        need to know.