Few important points (usually interview type Questions of salesforce ):
One Object can have only two Master-Detail relationships.
If we delete record A (First Master detail relationship is always primary) – then child record c will be deleted.
If we delete record B then in this case also child record C will be deleted.
If we delete record c then only C will be deleted , master record will not be deleted.
If child C has two Master record A and B, Where A is primary relation then Child record C will inherit the look and feel of Parent object A.
Lookup relationship does not auto-delete any record when the parent or child is deleted.