Arrange the following ecosystem in terms of their increasing productivity:
1. Grassland
2. Open ocean
3. Desert
4. Tropical rain forest
Select the correct answer code using the codes given below: Answer codes:
A. 3, 2, 1, 4
B. 1, 2, 3, 4
C. 3, 1, 2, 4
D. 4, 1, 2, 3
