Given scientific fact as input, generate the question from this fact such that it can be answered from the input.

[Q]: Respiratory acidosis is considered to be problematic because excess co2 in blood.
[A]: Why is respiratory acidosis considered to be problematic?

[Q]: Eyespots do the cells in the front of a volvox typically develop to help swim towards light.
[A]: What do the cells in the front of a volvox typically develop to help swim towards light?

[Q]: In a tropical rainforest, understory are ferns common.
[A]:
In a tropical rainforest, where are ferns common?