Cầu làm bằng... bìa các tông
Một cây cầu bắc qua sông được làm hoàn toàn bằng bìa các tông, vậy mà 20 người có thể đi qua được cầu trong cùng một lúc. Không tin bạn có thể tới Lyon (Pháp) để kiểm chứng.
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