Here's a riddle: If 96%got "I" right, and 83% got "Old" right, and the second clue is a 2 letter word starting with I and ending in O, how come only 75% have got that one?
Quito, Ulaanbaatar, and Zagreb are also capitals that have a unique starting letter. Could you narrow the scope of your clue? I like this quiz series though :)
Good quiz.