Canberra is called "bush capital"

The question asks why Canberra is called "bush capital". Option b, 'Why Canberra is called "bush capital"?', is the most grammatically correct and direct question. Option a has a grammatical error ('Canberras'). Option c uses 'Does' which is incorrect for a 'why' question. Option d uses 'are' with a singular subject 'Canberra'.