The Aboriginal people were displaced by the new European settlement.

The question asks if the Aboriginal people were displaced. Option 'a' directly asks this. Options 'b' and 'c' ask 'Why' and 'Where', respectively, which are not directly addressed by the statement. Option 'd' uses 'Did' which is grammatically incorrect with 'were displaced'. Therefore, 'a' is the most appropriate question that can be formed from the statement.