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

The bird ancestor that lived in trees developed wings, which is commonly associated with birds.
The bird ancestor that lived in trees developed what feature commonly associated with birds?

Embryos usually don't survive if they have extra or too few of these genetic units?
Embryos usually don't survive if they have extra or too few of these genetic units?

A diet rich in calcium and vitamin d may reduce the risk of osteoporosis and related bone fractures.

A diet rich in calcium and what vitamin may reduce the risk of osteoporosis and related bone fractures?