Productivity is the rate of production of biomass expressed in

i kcal m-3 yr-1              ii gm-2 yr-1             
iii g-1 yr-1                iv kcal m-2 yr-1

1. (ii)

2. (iii)

3. (ii) and (iv)

4. (i) and (iii)

Ans. (c) Productivity is the rate of production of biomass or organic matter by any trophic level per unit area over a time period. It s expressed/measured in terms of weight (e.g. gm/m2/yr2) or energy (e.g. kcal/m2/yr).
Page 243, XII NCERT