First Aid will be taught throughout the period tomorrow.
(This means the entire class period will only be on First Aid and nothing else.)
First Aid will be taught during the period tomorrow.
(This means that at some points during the class period First Aid will be taught.)
First Aid programmes will be held throughout the year.
Many soldiers were killed during the war.
Teo, Alvin. 2019. Confusing Grammar Explained. Singapore: Marshall Cavendish Education.