I fell asleep while trying to study and didn't wake up until the next morning.

My computer crashed and I lost all of my work that I had spent hours on.

My dog ate my textbook and notebook, so I had no material to refer to.

I got sick and was unable to focus on my homework due to not feeling well.

There was a power outage in my area, so I couldn't access any of my online resources or use my laptop.