Which of the following is arranged in decreasing order of extension (from the widest class to the narrowest)?

The order animal, vertebrate, bird, sparrow runs from the widest class to the narrowest.

Extension is the range of individuals a term applies to.

Animal is the broadest, covering every vertebrate and more.

Vertebrate is narrower, and bird narrower still within vertebrates.

Sparrow, a single kind of bird, has the smallest extension.

Each term is contained within the one before it, giving steadily decreasing extension.