This invention was invented by a 15-year-old boy with the help of his grandmother. Then he could stay outside and skate longer with his friends. His cars were warm and comfortable.
Many people believe that the first one was invented by 18-year-old Blaise Pascal in 1642 to help his father count taxes. It was used to add and subtract（加减） numbers. About 50 were made but they were not very popular 300 years later, they finally became popular. They have been popular ever since.
This invention helps people read, write and do "close work "after the age of 45. Without them, the world would be difficult for the people above 45.
Since it was invented, it has been recording the history of the world. It's also convenient for us to take some pictures about the unforgettable and amazing moments in our daily lives, and even keep them forever.
This invention can help people in the street. It looks like a tree standing beside the street. It directs（指挥） cars and trucks. Without it, the traffic would be terrible.
A. 
B. 
C. 
D. 
E. 
F. 
