【单选题】

Plastics are materials which are softened by heat and set into lasting form when shaped in a molD、Some are natural; some are semi synthetics as the result of chemical action on a natural substance; some are synthetic, built up from the constituents of oil or coal.All are based on the chemistry of carbon, with its capacity for forming chains. The molecules that compose them (monomers) link together in the setting or curing process to form chains (polymers), which give plastics their flexible strength. Some plastics retain their ability to be softened and reshaped; like wax, they are thermoplastiC、Others set permanently in the shapes they are given by heat and pressure; like eggs, they are thermosetting.

From industrial beginnings in the 19th century, plastics have struggled through a 120 years of glory, failure, disrepute and suspicion on the slow road to public acceptance. Now, at last, one can positively say that plastics are appreciated and enjoyed for what they are; that they make modern life richer, more comfortable and convenient and also more funny. Plastics are warm materials, sympathetic to the human touch and their transformation into things that come into contact with human beings is entirely appropriate.
The fact that there are plastics antiques comes as a shock to most people. How can a material that seems so essential in the 20th century, and one that is so much associated with cheap disposable products, have a history at all It is a young technology, and a great pan of the fun of collecting plastics is that beautiful pieces of historical interest can still be found very cheaply.
Why does the author mention "plastics antiques" in the third paragraph
A、Because some plastics objects are appreciated enough to be collecteD、
Because plastic copies of valuable antiques are relatively special.
C．Because collectors prefer plastic objects to other kinds of antiques.
D．Because dealers can afford the inexpensive plastic antiques.