It is estimated that some seven hundred million people about half the world's population are un able to read and write, and there are probably two hundred and fifty million more whose level of attainment(造诣、成就)is so slight that it barely qualifies a literacy(识字).
Recently the attack on illiteracy has been stepped up. A world plan has been drawn up by a committee of UNESCO experts in Paris, as part of the United Nations Development Decade, and an international conference on the subject has also been held. UNESCO stresses that functional literacy is the aim. People must learn the basic skills of responsible citizenship: the ability to read notices, newspapers, timetables, letters, price lists, to keep simple records and accounts, to sort out the significance of the information gathered, and to fill in forms.
The major areas of illiteracy are in Asia, and Central and South America. In Africa there are at least one hundred million illiterates, making up eighty to eighty-five per cent of the total population. In Europe the figure is about twenty-four million, most of them is Southern Europe, with Spain, Italy, Portugal, and Yugoslavia heading the list (the United Kingdom has about seven hundred thousand).
According to the estimate, the illiterate population in the world is ______.

A. two hundred and fifty million
B. one hundred million
C. about half of the total population in the world
D. seven thousand million