Which one of the following is true? O A. As a country becomes more prosperous, it experiences a higher birth rate. O B. Over the past century, the real price of food has risen, reflecting the pressure of population growth on food supplies. O C. Over the past century, the supply of food has grown more quickly than has the demand for food O D. Over the next half-century, it is expected that population growth in industrially advanced nations will outpace population growth in developing countries