WAEC Economics 1991 (August) Question 34

The productivity of labour does not depend only on its own effort and efficiency, but also on
I. the level of technical knowledge
II. the quality of other factors
III. racial qualities which allow persons from certain races to have good physique and be very active.
Which of the above statements is/are correct?

1. A.I only
2. B.I and II only
3. C.I and III only
4. D.II and III only
5. E.III only.