I think @mishabalyasin hit it there. The table mtcars is included in the datasets library, which is included in base-R. And is frequently used in learning examples.
(In fact, I think you can refer to mtcars without having to explicitly load library(datasets) )
As @o_gonzales mentions, this question comes from DataCamp's Writing Functions in R course by Hadley and Charlotte Wickham at www.datacamp.com/courses/writing-functions-in-r/. I personally think this particular course is really useful.
I also wanted to note community's homework policy: FAQ: Homework Policy. The gist is that one shouldn't post questions or materials verbatim. Homework inspired questions, like this one, are certainly welcome.