英语填空For thousands of years,people thought of glass as someth

英语填空
For thousands of years,people thought of glass as something beautiful to look at.Only recently 21 come to think of it as something look through.Stores 22 their goods in large glass windows.Glass bottles and jars 23 food and drink allow us to see the contents.Glass 24 spectacles(眼镜),microscopes（显微镜）,telescopes,and many other very useful and necessary objects,and glasses are used by people who cannot see 25 or by people who want to protect their eyes 26 bright light.Microscopes make tiny things larger 27 we can examine them.Telescopes make objects that are far away appear 28 closer to us.
However in recent years plastics have replaced glass 29 conditions where glass might be easily broken.There are new uses being developed for glass that were never imagined in the past.Perhaps the greatest 30 of glass is that its constituent(形成的) parts are inexpensive and can be found all over the world.
21.A.they B.do they C.they have D.have they
22.A.protect B.hide C.display D.set aside
23.A.hold B.held C.that hold D.that holding
24.A.used to make B.is used to make C.is used to making D.used to making
25.A.perfectly B.perfect C.perfection D.perfected
26.A.from B.in C.with D.beyond
27.A.so as B.as that C.so that D.such that
28.A.ever B.rather C.more D.much
29.A.under B.below C.within D.on
30.A.goodness B.advance C.advantage D.progress