A . it is cheaper ( 1) ____ silver

　　B . the coins were actually ( 2)____ silver

　　C . the silver in coins ( 3) ____ much more

　　Less than 40 years ago in the United States , it was common to change a one-dollar bill for a dollar ' s worth of silver . That is because ( 4) ____ . But those days are gone . There is no silver in today ' s coins . When the price of the precious metal rises above its face value as money, the metal will become more valuable in other uses . Silver coins are no longer in circulation because ( 5) _____ than their face value . A silver firm could find that ( 6) _____ by melting down coins than by buying it on the commodity markets . Coins today are made of an alloy of cheaper metals .

　　答案解析：

　　1.【答案】to obtain

　　【 解析】 it 為形式主語，不定式為真正主語，所以選to obtain 。