According to the passage, a large population will produce a chance for developing ______.

A．official attitudes to population and birth control vary from country to country
B．different countries have different customs and practices on birth control
C．decreasing birth rate may lead to unemployment in some countries
D．in some countries people think that they enjoy the right to have as many children as they like

A．inferior land must be cultivated
B．good land must work intensively
C．each person must produce less
D．Both A and B.