选择正确的句子将对话补充完整。 A. Why was it built? B. Who designed it? C. When was it built? A: Look, this is the Eiffel Towel, the tallest building in Paris. B: Wow! It looks great. . A: It was built in 1889. B: That's a long time ago. . A: It was built to celebrate the success of the French Revolution. B: I see. . A: It was designed by Alexander Eiffel, a French engineer.