试分析五十年后世界上可能出现的重大问题，内容应包括： 1．描述一下当前的隐患； 2．未来问题的出现形式及其严重性； 3．提供解决问题的可行性方案。 What do you think will be the world’s greatest problem in fifty years time

A．The effects of climate on the economy.
B．The relation between market prices and technological change.
C．The effect of shifts in supply and demand on market prices.
D．The increasing cost of skilled labor.

A．indicate that a wide variety of goods are affected
B．describe the two products that suffer the most
C．show how increased prices for agricultural products affected other prices
D．support the argument that cities suffer more than agricultural areas