21. —Can I look at the menu for a few more minutes before I decide? —Of course. _______ sir.
(A) Make yourself at home
(B) Enjoy yourself
(C) It doesn't matter
(D) Take your time

72．At one time, computers were expected largely to remove the need for paper copies of documents(文件) because they could be stored electronically. But for all the texts that are written, stored and sent electronically, a lot of them are still ending up on paper. It is difficult to measure the quantity of paper used as a result of use of Internet-connected computers, although just about anyone who works in an office can tell you that when e-mail is introduced, the printers start working overtime. “I feel in my bones this revolution is causing more trees to be cut down .” says Ted Smith of the Earth Village Organisation. Perhaps best sign of how computer and Internet use pushes up demand for paper comes from the high—tech industry itself ,which sees printing as one of its most promising new markets .Several Internet companies have been set up to help small businesses print quality documents from a computer .Earlier this week .Hewlett-Packard Co . announced a plan to develop new technologies that will enable people to print even more so they can get a hard copy of a business document , a medical record or just a one-line e-mail ,even if they are nowhere near a computer .As the company sees it , the more use of the Internet the greater demand for printers . Does all this mean environmental concerns (环境问题) have been forgotten? Some activists suggest people have been led to believe that a lot of dangers to the environment have gone away. “I guess people believe that the problem is taken care of ,because of recycling（回收利用）,”said Kelly Quirke,director of the Rainforest Action Network in San Francisco. Yet Quirke is hopeful that high—tech may also prove helpful .He says printers that print on both sides are growing in popularity. The action group has also found acceptable paper made from materials other than wood ,such as agricultural waste. The growing demand for paper in recent years is largely due to . (A)the rapid development of small businesses (B)the opening up of new markets (C)the printing of high quality copies (D)the increased use of the Internet

73．Environmentalists believe one possible way of dealing with the paper situation is . (A)to encourage printing more quality documents (B)to develop new printers using recycled paper (C)to find new materials for making paper (D)to plant more fast growing trees

74．Hewlett-Packard Co. has decided to develop new technologies because . (A)people are concerned about the environment (B)printers in many offices are working overtime (C)small companies need more hard copies (D)they see a growing market for printers

75．What would be the best title for the text ? (A)Computers and Printers (B)E-mail and the Business World (C)Internet Revolution and Environment (D)Modern Technology and New Markets

22. When flint _______ to the market, these products enjoyed great success. (A) introducing (B) introduced (C) introduce (D) being introduced

23. There were dirty marks on her trousers ______ she had wiped her hands. (A) where (B) which (C) when (D) that

24. The evening news comes on at Seven o' clock and ______ only thirty minutes. (A) keeps (B) continues (C) finishes (D) lasts

25.— Has Sam finished his homework today? —I have no idea. He ______ it this morning. (A) did (B) has done (C) was doing (D) had done

1.闪电时空气中有臭氧生成。下列说法中正确的是 (A)O3和O2互为同位素 (B)O2比O3稳定 (C)等体积O3和O2含有相同质子数 (D)O3与O2的相互转化是物理变化

2.同主族两种元素原子的核外电子数的差值可能为 (A)6 (B)12 (C)26 (D)30