Read this sentence from Neil deGrasse Tyson's preface to his book The Pluto Files:

Gathered here in one place is a record of Pluto's rise and fall from planethood, given by way of media accounts, public forums, cartoons, and letters I received from disgruntled schoolchildren, their teachers, strongly opinionated adults, and colleagues.
Why would this be considered an example of expository writing?
A. It argues that Pluto should not be considered a planet.
B. It fictionalizes the story of Pluto's history.
C. It gives an opinion of Tyson's book about Pluto.
D. It informs the reader about Pluto's planetary status

D. It informs the reader about Pluto's planetary status

Explanation:

There are four main types of writing: descriptive, persuasive, narrative and expository.

The main purpose of expository (sometimes named informative) writing is, as the name might suggest, to explain, define something or inform the readers on a certain topic providing an explanation.

This particular sentence informs us about "Pluto's rise and fall from planethood" which means that it is no longer considered a planet.

In that way, it explains us Pluto's planetary status, which makes this an example of expository writing.

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