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