Arrange the following ecosystems in increasing order of their mean NPP (tons/ha/year).
(A) Tropical deciduous forest
(B) Temperate coniferous forest
(C ) Tropical rainforest
(D) Temperate deciduous forest
A. `BltAltDltc`
B. `DltBltAltC`
C. `AltCltDltB`
D. `BltDltAltC`