In 1798 the political economist Malthus predicted that in time mankind would face starvati

on, having outgrown the available food supplies. Today, a century and a half later, there are still experts who forecast the same global disaster—unless urgent measures are taken to prevent it. By the end of the present century there may well be over five thousand million people living on this globe, an increase of over fifty percent on todays figure. In order to keep pace with this increase in mankind the farmers of the world will have to step up their production of food by at least two percent every year. Such a rate of increase has never been maintained in any country by conventional methods of agriculture, despite modern mechanization and the widespread use of fertilizers. There are no large worthwhile reserves of potential farmland remaining, and good fertile land is continually being changed into industrial use. Moreover, erosion of the soil takes a constant toll (损失). Intensive research, carried out over many years in all manners of climate conditions, has produced a revolutionary method of growing crops without using any soil at all. Hydroponics (水栽 法), as this technique is called, may well be the answer to all our food worries; already it has accomplished wonders in producing huge crops. Hydroponics was once a complicated and expensive business, now it is well out of the experimental stage. Labor costs are far lower than when normal methods of agriculture are employed. In fact, it is a completely automatic system. There is no hard manual work, no digging or ploughing, and no weeding to speak of. Yields can be far higher than they are in soil.

Which of the following best sums up the whole passage？

A．Malthus" prediction has been proved to be correct by modern experts.

B．Hydroponics is a new development in agriculture.

C．Hydroponics may be the answer to the world food shortage in the future.

D．Conventional methods of agriculture should be improved so as to step up food production by two percent every year.