TOEFL Listening: TPO-TOEFL阅读TPO - YAM1KMA9NXNS4LTQN$

What function does paragraph 3 serve in the organization of the passage as a whole? A. It contrasts the development of iron technology in West Asia and West Africa. B. It discusses a non-agricultural contribution to Africa from Asia. C. It introduces evidence that a knowledge of copper working reached Africa and Europe at the same time. D. It compares the rates at which iron technology developed in different parts of Africa.