Final answer:
The most ironic option is (b) A politician from a multicultural background representing the electorate, as it directly contradicts the White Australia policy's aim to maintain a white population.
Step-by-step explanation:
Regarding the statement, "It is one of his greatest ironies that the seat named after the architect of the White Australia policy has become one of the most multicultural in the country," the option that best exemplifies irony is (b) A politician from a multicultural background representing the electorate. This is because it is a direct contradiction to the original intent of the policy designed by the architect, which was to limit nonwhite immigration, thereby maintaining a predominantly white population. Hence, a politician of nonwhite or diverse ethnic background in a position of power within that electorate highlights a stark contrast to the original policy objectives.
The White Australia policy, established in 1901, sought to limit immigration to predominantly white persons from the United Kingdom, and it offered subsidies to British citizens to relocate. It was not until 1973 that these policies were completely dismantled. The election of a multicultural politician in the Barton electorate is therefore an ironic twist to the electorate's namesake, Edmund Barton, who was instrumental in implementing the White Australia policy.