In "Monty Python and the Holy Grail," how many questions must a knight answer to cross the Bridge of Death?

Appearing in the film "Monty Python and the Holy Grail' (1975), if someone wants to go over the Gorge of Eternal Peril, he has to cross the Bridge of Death. Prior to crossing, he or she has to answer three scary and mean questions from the bridge keeper. If the person fails, then the person is magically thrown into the gorge.

Sir Lancelot managed to cross the bridge. Seeing how easy the questions are, Sir Robin eagerly goes second. His first two questions are the same as for Lancelot, but the third isn't as easy: what is the capital of Assyria? Robin says he doesn't know, and a moment later he was thrown into the gorge. Sir Galahad, the chaste, goes third. His questions are all the same as the ones for Lancelot. He answers the same as Lancelot, saying however that his favorite color is blue. He then quickly tries to correct himself and say yellow, that doesn't save him from being thrown into the gorge for his little mistake. King Arthur is the next to answer. His first two questions are the same as for Lancelot, Robin and Galahad, but the third is: "What is the airspeed velocity of an unladen swallow?" Arthur asks which kind of swallow: African or European, and when the bridge keeper answers "I don't know that", he is thrown into the gorge himself.

After this, Arthur and the last knight, Sir Bedevere, the wise, cross the collapsing, old Bridge of Death without any more questions.

The film in this instance is said to obviously be a good parody of King Arthur's myth.