Which sentence contains a preposition?

British soldiers attacked the unarmed colonists.

He and other colonists had gathered.

Our country's past interests me greatly.

I read a book about the patriot Crispus Attu

I read a book about the patriot Crispus Attu

The word "about " is the preposition.

A preposition is a word governing, and usually preceding, a noun or pronoun and expressing a relation to another word or element in the clause, as in "the man on the platform," "she arrived after dinner," "what did you do it for?".

A list of prepostiion includes: in, down, outside, inside, after, before, for and about (but there's a lot more)

And you can see the bold word above, that is the preposition in "I read a book about the patriot Crispus Attu"

So the last sentence is correct