Final answer:
Filling a bomb with pure oxygen instead of air results in a more powerful and efficient explosion due to oxygen's superior support of combustion.
Step-by-step explanation:
In the context of filling a bomb, the reason pure oxygen is used instead of air is because oxygen supports combustion more effectively than air. By using pure oxygen, the bomb can achieve a more powerful and efficient explosion. In contrast, if air were used to fill the bomb, it would contain other gases like nitrogen and trace amounts of other elements. These gases would dilute the oxygen and make the combustion less intense. Therefore, skipping the step of filling the bomb with pure oxygen would result in a less powerful explosion.