2.He happened on the book in a secondhand bookstore.
他在旧书店里偶然这本书。
3.Fleming discovered penicillin by accident in 1928.
弗莱明在1928年偶然青霉素。
4.In 1895, Wilhelm Roentgen accidentally discovered that a cathode-ray tube could make a sheet of paper coated with barium platinocyanide glow, even when the tube and the paper were in separate rooms.