There are so many people that the tickets are all sold out!
Luckily we got the last two.
Look, Danny. The Four Great Inventions!
Gunpowder, compass, the paper making, and the printing.
I really admire those who made such great inventions!
May, I don't see why they are great. They are just simple things.
They look simple today. But they were milestones in their times.
Milestones? May, you must be kidding.
Just think Bill Gates, those inventions are as important as the windows system.
Well, I suppose the ancient inventors made a lot of money out of them.
No, quite the contrary.
Why? Didn't you say that they were milestones?
Yes, but they went to the public without any patent protection.
Well, their inventors were not as clever as Bill Gates.