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

Are humans a new or old species on the earth?
Are humans a new or old species on the earth?

A(n) an ionic bond forms when the metal sodium gives up an electron to the nonmetal chlorine.
What forms when the metal sodium gives up an electron to the nonmetal chlorine?

Gastrin signals the secretion of gastric acid.
What signals the secretion of gastric acid?