Within 80 years, some scientists estimate,

问题：

Within 80 years, some scientists estimate, the world must produce more than eight times the present world food supply. The productiveness of the sea raises our hopes for an adequate food supply in the future. Aided by men of science, we have set forth to find out that 70 percent of the earth remains unexplored--the ocean depths. Thus, we may better discover and utilize the sea’s natural products for the world’s hungry.

It is fish protein concentrate that is sought from the seas. By utilizing the unharvested fish in United States waters alone, enough fish protein concentrate can be obtained to provide supplemental animal protein for more than one billion people for one year at the cost of less than half a cent per day per person. The malnutrition of children is terribly tragic. But the crime lies in society’s unrestrained breeding, not in its negligence in producing fish powder. But wherever the population projects are carefully considered, the answer to the problem is something like this: There are few projects that could do more to raise the nutritional level of mankind than a full-scale scientific effort to develop the resources of the sea. Each year some thirty million tons of food products are taken from the sea, which account for 12 percent of the world’s animal proteins. Nations with their swelling populations must push forward into the sea frontiers for food supplies. Private industry must step up its marine research and the federal government must make new attacks on the problems of marine research development. There is a tone of desperateness in all these designs on the sea.

But what is most startling is the assumption that the seas are an untouched resource. The fact is that the seas have been, and are being, hurt directly and indirectly, by the same forces that have abused the land. In the broad pattern of ecological relationships the seas are not separable from what happens on the land. The poisons that pollute the soil and the air bring in massive doses into the "continental shelf" waters. The dirt and pollution that spills from our urban sewers and industrial out falls despoil our bays and coastal waters. All the border seas are already heavily polluted by the same exploitation drives that have undermined the quality of life on land.

The author’s primary concern is that（）

A. the oceans will help to provide enough food for the world in the future

B. thirty million tons of food products are taken from the sea every year

C. city sewers are pouring forth polluted matter into bays and coastal waters

D. a steady increase in population will result in more hungry mouths to feed