The correct answer is: A) Mean years of schooling.
Mean years of schooling is a measure of the average number of years of schooling that a person has completed. It is calculated by taking the total number of years of schooling completed by all people in a country and dividing it by the total population.
Mean years of schooling is an important indicator of the level of education in a country. It is used to measure the progress that a country is making in terms of education and to compare the level of education in different countries.
The other options are not used in the education component of the HDI.
- Teacher-student ratio is a measure of the number of students per teacher in a school. It is calculated by dividing the total number of students in a school by the total number of teachers.
- School infrastructure is the physical facilities of a school, such as the buildings, classrooms, and equipment.
- Dropout rates are the percentage of students who drop out of school before completing their education.
These three options are not used in the education component of the HDI because they do not measure the level of education in a country. They measure other things, such as the quality of education or the access to education.