A、The stories about some important technological inventions. B、The history of the 19th and early 20th centuries. C、The future of

W: Can you tell me a little bit about your current project? What are you working on now?
M: (19)I’m writing a book about some of the most important technological inventions of the 19th and early 20th centuries. It’s about how things like the typewriter or the fax machine were developed, and so on.
W: That sounds really interesting.
M: It is. It is fascinating. The personalities behind the inventions are particularly fun to read about. Like. . . a lot of inventors were amateurs, and some of them were considered to be crazy!(20)But they had this incredible determination. They believed absolutely in what they were doing.
W: But then they also discovered things by accident?
M: Oh, yes, like the microwave oven. The microwave oven was actually developed from the power tube that drives a radar machine. One day, this scientist—Percy Spencer—was standing next to a power tube, and he had a chocolate bar in his pocket. (21)And the chocolate melted. So the next day he came in with popcorn, and guess what happened?
W: Pop.
M: Yes. But some products were just not in the right place at the right time. The classic example of that was the fax machine. I bet you didn’t know we had fax machines before we had telephones.
W: Really?
M: Yes. The French were using very effective fax machines in the 1860s, before the telephone, in fact. But the idea never took off. At that time, people were more interested in the telegraph.
W: That’s amazing.
M: Yes. (22)People have to be ready for a new thing before they’ll accept it.
19. Q: What is the man’s current book about?
20. Q: What does the man think of the inventors?
21. Q: What happened to Percy Spencer when he stood next to a power tube?
22. Q: What can we learn from the example of fax machine?