"Lateralization" refers to the specialization of one of the cerebral hemispheres to handle a particular function. Biological psychologists know that the left cerebral hemisphere is somewhat lateralized or specialized for language from research,
including research:

1) On split-brain patients
2) on subjects with intact brains
3) using fMRI (functional magnetic resonance imaging)
4) using brain imaging techniques
5) all of the above answers are correct