Python's Meta classes can be used in various ways to customise the default behaviour of Django or other Python libraries. Select below all the correct uses of the Meta class;

a. Customise the behaviour of Django's ORM mechanism on particular models

b. Customise the behaviour of model serialisers in the django-rest-framework

c. Customise the behaviour of model forms in forms.py

d. Customise the behaviour of HTTP request headers in request.META

e. Customise the behaviour of regular expressions using meta characters