【正文】 r. Stick four toothpicks around the middle of the seed. 2. Fill the jar almost to the top with water that is just slightly warm. Rest the toothpicks on the top of the jar. The more pointed end of the seed should be in the water while the flatter end should face upward. 3. After that, you will have to wait for three or four weeks. During that time, be sure to add just enough water to replace the water that evaporates into the air. The bottom of the seed should always be just below the water’s surface. The thin brown skin that covers the seed will crack(破裂 ) open. Roots will start growing out of the bottom of the seed. Leaves will start growing at the top. 4. When the roots are about three inches long, fill a flowerpot with soil and plant the seed. Make sure that the seed is pletely covered by soil and that the young leaves are above the soil. 5. Find a sunny spot for the plant. Water it every few days to keep the soil moist (潮濕的 ). Watch it during the next few months. Your avocado plant will grow a tall, straight stem (莖 ) and large oval leaves. 44. The main idea of the first paragraph is to ______. A. tell us how to grow an avocado plant B. give us a brief introduction to avocados C. tell us the shape and color of avocados D. tell us that avocado is a fruit 45. Which of the following statements is NOT true according to the passage? A. The two points of the seed are of the same shape. B. The soil in the flowerpot should neither too dry nor too wet. C. We’d better use ripe avocados to make some guacamole. D. The most popular way to use avocados is in guacamole. 46. The word “evaporates” in the fourth paragraph means _______. A. turns into ice because of cold weather B. bees very hot by the sun heat C. turns into other things because of chemical change D. bees vapor and disappear 47. How long will the thin brown skin that covers the seed crack open? A. 1 or 2 weeks. B. 2 or 3 weeks. C. 3 or 4 weeks. D. a few days. D The scientist from the Lockheed Space Company work in Felton, California, with the help of a puter. But the puter is placed in Sunnyside, about 80 kilometers away. What scientists input (輸入 ) is sent by telephone lines to the puter, and after a time, copies of the designs are needed back in Felton as quickly as possible Lockheed people have tried several ways of sending the prints, but the most effective seems to be by pigeon. Are pigeons really used to carry messages in these days? They are, and they send the prints faster and cheaper than any other way. Human messengers are much more expensive and slower than the pigeons. The road to Felton goes through the mountains, and the driving is not easy. An electronic printout (電子打印輸 出 ) system could do the work in Felton, but at a cost of 10 dollars a print. Pigeons carry the designs for about 1 dollar each. Now Lockheed people have ten pigeon messengers. The pigeons do the work, and they have made Lockheed more famous. You can often read the news about pigeons in the newspapers around the world. 48. The passage is mainly about ___________________. A. Felton, California B. the scientists C. how to work with puters D. sending prints by pigeon 49. This story is unusual because pigeons ____________________. A. don’t like carrying things B. are often expensive to keep C. seem out of place in the space age D. aren’t friendly to the scientists 50. Something that’s effective ________________________. A. usually costs more B. is something that works C. is often unhappy D. is often done by animals 51. Which happened first? A