Final answer:
To change fluorine-19 into another isotope, bombarding it with neutrons would be the correct method as it alters the neutron count while keeping the number of protons constant.
Step-by-step explanation:
The question asks which action would change fluorine-19 into another isotope. The atomic number for the element fluorine is 9, which means it has 9 protons, and its mass number is 19, indicating that it has 19 protons and neutrons combined. Considering that the number of protons is constant for a given element, the only way to change fluorine-19 into another isotope of fluorine is by altering the number of neutrons. Therefore, bombarding it with neutrons would increase the neutron count and produce a different isotope of fluorine.