[简答题]The comparable dates for the computer are harder to tie down, but the first big computer, based on vacuum valves, was built in 1946. The transistor—the first semicon ductor device—was invented at Belt Laboratories in 1948. The first patent for an integrated circuit was filed in 1959. Now, in 1999—50 years after the first one was built—around half of American households own a computer. The pace of introduction has been similar to that of the car.

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Gold used in jewelry is mixed with harder metals to add strength and durability. The metals added can also be used to change gold’s color, giving it a fashionable rose or white tint, or to lighten or darken the natural yellow tone of pure gold. Mixtures like these, of less costly metals with more valuable ones, are called alloys. Copper and silver are the most common metals mixed with gold to make yellow gold jewelry. White gold is usually made with an alloy of gold and nickel.
The measure of gold’s purity is called a karat. The higher the karat rating, the higher the amount of pure gold: 24 karat is pure gold, 18 karat is 75% pure gold, 14 karat is 58.5% pure gold, and 9 karat is 37.5% pure gold. All other things being equal, the higher the percentage of pure gold used in the alloy, the more valuable and expensive the jewelry will be.
Gold jewelry pieces are usually stamped with a marking to identify the karat amount. While gold that is 24K is too sof
A. Although gold is very valuable, it is also very expensive.
B. Gold jewelry is stamped with its karat weight.
C. Gold jewelry is made using alloys.
D. Colored gold is more valuable than white gold.

[单项选择]With the introduction of the computer, libraries today are quite different from ______ they were in the past.
A. that
B. what
C. which
D. those

[单项选择]Telecommuting--substituting the computer for the trip to the job--has been ______ a solution to all kinds of problems related to office work.
A. hailed as
B. drawn out
C. borne out
D. lodged in

[单项选择]On that trip, the loneliness was a little harder to handle, so I brought along our puppy to keep me （）
A. company
B. partner
C. attendant
D. fellowship

[单项选择]A. The computer doesn’t work. B. The computer is very helpful.
C. He felt tied. D. It is over there.

[单项选择]The computer doesn’t work well, so something （） wrong.
A. can have gone            
B. should have gone
C. must have gone            
D. ought to have gone

[单项选择]The computer doesn’t work. We’ll have to have it （）.
A. to repair
B. repaired
C. repairing