A pre-compiled module has been moved to /lib/modules/<kernel-version>, but ‘modprobe -a
<module-name>’ fails to load it. What needs to be done to enable usage of this module?

A.
make modules_install must be run.

B.
depmod must be run.

C.
The kernel must be re-compiled.

D.
modules.conf or modprobe.conf must be edited.

E.
The system must be rebooted.

Explanation:
From the man pages:
depmod – program to generate modules.dep and map files.
depmod creates a list of module dependencies by reading each module under /lib/modules/version
and determining what symbols it exports and what symbols it needs. By default, this list is written to
modules.dep, and a binary hashed version named modules.dep.bin, in the same directory. If
filenames are given on the command line, only those modules are examined (which is rarely useful
unless all modules are listed).
depmod also creates a list of symbols provided by modules in the file named modules.symbols and
its binary hashed version, modules.symbols.bin.
modprobe expects an up-to-date modules.dep.bin file (or fallback human readable modules.dep
file), as generated by the corresponding depmod utility shipped along with modprobe (see
depmod(8)). This file lists what other modules each module needs (if any), and modprobe uses this
to add or remove these dependencies automatically.