I decided to check back on the Tokyo Metro 10th Anniversary website because I figured they might change the quiz and the paper model that you can unlock each month, and so they did! ;o)
Again, you could guess your way through the six true-or-false quiz if you don't understand Japanese (a red "正解" after choosing your answer means the answer was correct, a blue "不正解" means it was wrong - or you can look at the answers at the bottom of this post);
If you got all six answers right, at the end you will see a blue button near the bottom saying "プレゼントをダウンロード" that will let you download the PDF parts file (otherwise it will say "もう一度チャレンジ！" and take you back to the beginning so you can try again).
Good luck and have fun!
(Tokyo Metro May 2014 Test answers: Q1o, Q2o, Q3x, Q4o, Q5o and Q6x)