I studied hard to pass my O Level exams.

I can't imagine my life without you.

I followed the will-o'-the-wisp through the dark forest.

Please send the package c/o John.

He wore a tam-o'-shanter to keep his head warm in the cold Scottish weather.

I carved a spooky jack-o'-lantern for Halloween.

The prisoner was punished with a cat-o-nine-tails.

I will meet you at o'clock

I always enjoy the beautiful sight of the four-o'clock flowers blooming in my garden at sunset.

He always has a five-o'clock shadow by the end of the day.