Before the 1500’s, the western plains of North America were dominated by farmers. One group, the Mandans, (31) in the upper Missouri River country, primarily in present-day North Dakota. They had large villages of houses (32) close together. The (33) arrangement enabled the Mandans to protect themselves more easily (34) the attacks of others who might seek to (35) some of the food these highly capable farmers stored from one year to the next. The women had primary responsibility for the fields. They had to exercise (36) skill to produce the desired results, (37) their northern location meant fleeting growing seasons. Winter often lingered; autumn could (38) by severe frost. For good measure, during the spring and summer, drought, heat, hail, grasshoppers, and other (39) might await the wary grower. Under (40) conditions, Mandan women had to grow maize capable of weathering (41) They began (42) it appeared feasible to do so in the spring. Harvesting proceeded in (43) stages. In August the Mandans picked a small amount of the crop (44) it had matured fully. This green corn was boiled, dried, and shelled, with some of the maize (45) for immediate consumption and the reststored in (46) bags. Later in the fall, the people picked the rest of the corn. They saved the best of the harvest for seeds or for trade, (47) the remainder eaten right away or stored for later use in underground reserves. With appropriate (48) of the extra food, the Mandans protected themselves (49) the disaster of crop failure and accompanying (50) .
A. frustrations
B. pets
C. insects
D. storms
(1)计算功能重要性系数。(2)计算功能系数、成本系数、价值系数、选择最优设计方案。
When you choose a freezer, remember it’s probably going to be with you for a long time. No single style or size is best, so it’s important to know which freezer is right for your needs. First, decide if you want an upright or chest model. Uprights are more convenient. Their storage space is more accessible and they take up less floor area. However, chest models are more energy-efficient because less cold air escapes when they are open. If you’re buying an upright, you’ll have to choose between frostless or manual defrost. Chest freezers are always manual. Frostless freezers automatically defrost at preset intervals and remove the water. Manual models must be defrosted by hand every few months or whenever frost accumulates to about a quarter of an inch. To help your freezer reach a ripe old age, try to find a spot that’s cool, dry, and away from drafts. Drafts and heat will raise the freezer’s cabinet temperature and make it work harder to keep cool. That means wasted energy and a shortened compressor life. Dry air is important because high humidity can cause the freezer to rust outside and frost up inside. With proper care, a freezer can serve you for 15 years or more. Frostless models require less care than manual defrost freezers. The interior of a frostless unit should be washed periodically with warm water and baking soda or a mild soap, rinsed, and dried. To get the most from your freezer, check regularly to make sure it’s providing a true zero-degree temperature. Keep the freezer at least three-quarters full. The emptier it gets, the more energy is wasted. If more than three pounds of food per cubic foot of storage space is added every 24 hours, the resulting high or low temperatures can damage the food. Which statement best describes the main idea of the passage
A. It discusses the advantages and disadvantages of freezers.
B. It tells the most economical ways to use a freezer.
C. It explains how to defrost a manual-defrost freezer.
D. It offers advice about choosing and caring for a freezer.
Before the 1500’s, the western plains of North America were dominated by farmers. One group, the Mandans, (31) in the upper Missouri River country, primarily in present-day North Dakota. They had large villages of houses (32) close together. The (33) arrangement enabled the Mandans to protect themselves more easily (34) the attacks of others who might seek to (35) some of the food these highly capable farmers stored from one year to the next. The women had primary responsibility for the fields. They had to exercise (36) skill to produce the desired results, (37) their northern location meant fleeting growing seasons. Winter often lingered; autumn could (38) by severe frost. For good measure, during the spring and summer, drought, heat, hail, grasshoppers, and other (39) might await the wary grower. Under (40) conditions, Mandan women had to grow maize capable of weathering (41) They began (42) it appeared feasible to do so in the spring. Harvesting proceeded in (43) stages. In August the Mandans picked a small amount of the crop (44) it had matured fully. This green corn was boiled, dried, and shelled, with some of the maize (45) for immediate consumption and the reststored in (46) bags. Later in the fall, the people picked the rest of the corn. They saved the best of the harvest for seeds or for trade, (47) the remainder eaten right away or stored for later use in underground reserves. With appropriate (48) of the extra food, the Mandans protected themselves (49) the disaster of crop failure and accompanying (50) .
A. adversary B. adversarial C. adversity D. advertency