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

Q: Diffraction is the phenomenon in which light and sound waves become circular at the point source of a barrier.

A: What is the phenomenon in which light and sound waves become circular at the point source of a barrier?
****
Q: Like mitochondria, plastids contain their own dna.

A: Like mitochondria, plastids contain their own what?
****
Q: Convection currents causes cumulus clouds to grow upward.

A:
What causes cumulus clouds to grow upward?
****