Odpowiedź:
1) It is surprising that 3-D printing was invented in the early 1980s.
2) Hull was working for a company that produced ultraviolet lamps when he thought of his invention.
3) Hull was designing his 3-D printer at night.
4) It was difficult for Hull to show people his invention because the first model of his 3-D printer was very large and heavy.
5) Car industry decided to use Hull's 3-D printers.
