How is the source code for the main Linux kernel modules distributed?

How is the source code for the main Linux kernel modules distributed?
A . It is included with the Linux kernel source code.
B . The kernel modules are downloaded on demand as they are used during compilation.
C . The kernel modules have their own release cycle and can be maintained separately from the Linux kernel source.
D . It is provided as a separate download alongside the Linux kernel source code of the same version.

Answer: A