Bangladesh is arguable - independence was declared on 25 March 1971 but the first countries to recognise it made the step on 6 December 1971. Probably fair enough given that the quiz 'recognises' both Taiwan and China.
that last part is key. most good historical quizzes don't give a crap if it was recognized by the international community. they aren't taking the ignorant perspective of people of the era, they are making a reasonable guess at if its independent compared to other countries they consider independent.