As goods and services improved, people were persuaded to spend their money on changing from old to new, and found the change worth the expense.  When an airline equipped itself with jets, for example, its costs (and therefore air fare) would go up, but the new planes meant such an improvement that the higher cost was justified. A new car (or wireless, washing machine, electric kettle) made life so much more comfortable than the old one that the high cost of replacement was fully repaid.  Manufacturers still cry their goods as persuasively as ever, but are the improvements really worth paying for? In many fields, things have now reached such a high standard of performance that further progress is very limited and very, very expensive. Airlines, for example, go to enormous expense in buying the latest jets , in which vast research costs have been spent on  ly small improvements. If we abandon these vast costs we might lose the chance of cutting minutes away from flying times; but wouldn't it be better to see airfares drop dramatically, as capital costs become  ly insignificant? Again, in the context of a 70 m. p. h. Limit, with lines of cars traveling so close as to control each other's speeds, improvements in performance are actually irrelevant; improvements in handling are unnecessary, as most production cars grip  the road perfectly, and comfort has now reached a very high level. Small improvements here are unlikely to be worth the thousands that anybody replacing an ordinary family car every two years may have spent on them. Let us instead have cars -- or wireless, electric kettles, washing machines, television sets -- which are made to last, and not to be replaced. Significant progress is obviously a good thing, but the insignificant progression from model-change to model-change is not. In the case of cars, the author advises that we   _  .
cancel the speed limit further improve their performance change models every two years improve their durability
Question: As goods and services improved, people were persuaded to spend their money on changing from old to new, and found the change worth the expense.  When an airline equipped itself with jets, for example, its costs (and therefore air fare) would go up, but the new planes meant such an improvement that the higher cost was justified. A new car (or wireless, washing machine, electric kettle) made life so much more comfortable than the old one that the high cost of replacement was fully repaid.  Manufacturers still cry their goods as persuasively as ever, but are the improvements really worth paying for? In many fields, things have now reached such a high standard of performance that further progress is very limited and very, very expensive. Airlines, for example, go to enormous expense in buying the latest jets , in which vast research costs have been spent on  ly small improvements. If we abandon these vast costs we might lose the chance of cutting minutes away from flying times; but wouldn't it be better to see airfares drop dramatically, as capital costs become  ly insignificant? Again, in the context of a 70 m. p. h. Limit, with lines of cars traveling so close as to control each other's speeds, improvements in performance are actually irrelevant; improvements in handling are unnecessary, as most production cars grip  the road perfectly, and comfort has now reached a very high level. Small improvements here are unlikely to be worth the thousands that anybody replacing an ordinary family car every two years may have spent on them. Let us instead have cars -- or wireless, electric kettles, washing machines, television sets -- which are made to last, and not to be replaced. Significant progress is obviously a good thing, but the insignificant progression from model-change to model-change is not. In the case of cars, the author advises that we   _  .
A. cancel the speed limit
B. further improve their performance
C. change models every two years
D. improve their durability
Answer: