Secondary education was provided from 15 years to___________?

A. 18 years
B. 17 years
C. 16 years
D. 20 years

It was an intellectual education. After the completion of the 14 years of training, the poor students ended their education and join apprenticeship of a trade. But the rich students continued their education under a philosopher teacher or Sophists. They were taught subjects like sophistry, geometry, astronomy and also rhetoric(art of speaking and writing).