Why is it important to write C$++$ code that is split into separate source files?

I. Objects in C$++$ can only be defined using separate source files.

II$.$ It is more efficient to compile since only files that have changed need to be recompiled.

III. It lessens the problem of multiple team members needing to simultaneously edit the same source file.

Question $8$ options:

I, II

I, III

II$,$ III

I, III