题目内容
（请给出正确答案）
A、用最小元素法求得的初始调运方案一定唯一
B、用元素差额法求得的初始调运方案一定唯一
C、不存在闭回路的一组解就是基本可行解
D、以上说法均不对
简答题官方参考答案
（由简答题聘请的专业题库老师提供的解答）
更多“m个产地n个销地的平衡运输问题中（)。”相关的问题
A、有
个非零的基变量
B、系数矩阵中有个列向量线性无关
C、模型包含
个变量,
个约束方程
D、模型最多只有
个独立方程
"Homemakers go out of their way to save pennies at the store and then don't realize that waste of edible (可食用的) foods adds up much more at home," said Dr. Rathji. He was one of about 100 food experts who met in Boise for a conference on food waste and ways to prevent it.
American families throw out between 8% and 20% of edible food at a cost of $4.5 billion per year. That's almost as much as the federal government spends every year for food stamps and child nutrition programs.
He found that food items which are costly and in short supply tend to be wasted more. During the 1973 meat shortage, meat waste increased to 9%, compared with 3% in 1974 and 1975. Sugar and sugar products waste jumped to 19% in 1975, when sugar prices doubled from the previous year.
Dr. Rathji theorizes that high prices force consumers to experiment, sometimes buy in large quantities. In the case of meat, sometimes low-priced cuts for unappetizing varieties are purchased, consumers then tend to waste more.
His theory is that the more variety in food bought, the more wasted. Regular bread is wasted at about a 10% rate, but specialty breads and rolls are wasted at a 20% rate.
If people are eating the same thing every day, they learn how to manage it. But if you're trying to pull something out of the cookbook every night, that's bound to be some waste.
Another finding is that lower income families waste less food than middle and upper income families. And the study found that dog food, which accounts for 8% of a shopping cart, is rarely wasted. Fresh produce and frozen items are more likely to be wasted.
The study also showed people with the most knowledge of safe, edible food waste the least. Much food is tossed out because a homemaker suspects it is spoiled when it is not.
1、Large quantities of food are thrown out because a homemaker____.
A、thinks they are not delicious
B、 says they taste bitter and hot
C、thinks they smell bad
D、 suspects they are spoiled when they are not
2、American families throw out between____of edible food every year.
A、5%～8%
B、 8%～10%
C、 20%～28%
D、8%～20%
3、When sugar prices doubled, waste of sugar____.
A、went down
B、went up
C、stayed the same
D、was cut in half
4、Which of the following statements is true?____
A、American housewives are not good homemakers.
B、Upper-income families are more wasteful than lower-income ones.
C、American families throw away almost as much food as they consume.
D、Americans waste a great deal of dog food.
5、When do American families waste more food?____
A、When prices are high.
B、When food is scarce.
C、When they think it is spoiled.
D、All of the above.
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个约束
