The population of the United States is only 6% of the world’s population, but Americans (21) one third of all the energy (22) in the world. This fact alone says that Americans need to use less energy. And because the price of energy had been rising very rapidly (23) the limited supplies of oil in particular, Americans are becoming aware to the need to (24) energy. In California we have a California Energy Commission which has set up in the past five years to (25) plan for our future energy use. We have (26) laws in California to help us conserve energy. First of all, our houses in California have been very (27) of energy in the past. They were not (28) very carefully and so the heat would go out of the house very rapidly. Now we require that the homes have a (29) level of insulation, and so the homes built now are much more (30) .
(31) , in transportation (32) a
A. effective
B. sufficient
C. efficient
D. deficient
The computer virus is an outcome of the computer overgrowth in the 1980s. The cause of the term "computer virus" is the likeness between the biological virus and the evil program infected with computers. The origin of this term came from an American science fiction The Adolescence of P-l written by Thomas J. Ryan, published in 1977. Human viruses invade a living cell and turn it into a factory for manufacturing viruses. However, computer viruses are small programs. They expand by attaching a copy of themselves to another program. Once attached to the host program, the vi ruses then look for other programs to "infect". In this way, the virus can spread quickly throughout a hard disk or an entire organization when it infects a LAN or a multi-user system. The timing of the attack can be linked to a number of situations, including a certain time or date, the presence of a particular file, the security level of the user, and the number of times a file is used. Like
A. It is a virus that causes great damage.
B. It is a virus that once infected the IBM’s computer system.
C. It is a virus that carries a Christmas greeting.
D. It is a virus that causes no harm to the computer systems.
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