Decomposers, like fungus.
C. Shield Volcano.. think of Hawaiian volcanoes,they are basaltic eruptions, very effusive and unexplosive and are characterised by slow lava movement and very little tephra from the eruption. The basalt erupted is very hard, dense rock and so can be built up easily.
I think its A. If you had options like mine
The investment in education and training for people.
Product A with 300 calories and 19 grams of protein