According to Plato higher education started from the age of 21 years and lasted till__________?

A. 35 years
B. 30 years
C. 60 years
D. 50 years

Students achieved more advanced knowledge at this stage, mathematics, mathematics, philosophy of literature for 10 years. The pupils should get the knowledge of dialectic for 5 years.

The correct answer to the question: "According to Plato higher education started from the age of 21 years and lasted till__________?" is "35 years".