Read the following passage and mark the letter A, B, C, or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 17 to 21.

If you're an environmentalist, plastic is a word you tend to say with a sneer or a snarl. It has become a symbol of our wasteful, throw-away society. But there seems little doubt it is here to stay, and the truth is, of course, that plastic has brought enormous ______(17), even environmental ones. It‟s not really the plastics themselves that are the evil - it's the way society chooses to use and ______(18) them.

Almost all the 50 or so different kinds of modern plastic are made from oil, gas or coal ─ non-renewable natural resources. We ______(19) well over three million tones of the stuff in Britain each year and, sooner or later, most of it is thrown away. A high ______(20) of our annual consumption is in the form of packaging, and this ______(21) about seven percent by weight of our domestic refuse.