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

Respiratory acidosis is considered to be problematic because excess co2 in blood.
Why is respiratory acidosis considered to be problematic?

The most significant connection between the cerebellum and the rest of the brain is at the pons.
Where is the most significant connection between the cerebellum and the rest of the brain?

A(n) echo is heard when sound waves bounce back from a surface that they can't pass through.

What is heard when sound waves bounce back from a surface that they can't pass through?