【单选题】The Development of Rubber Here is the story of rubber. From the earliest time it was common knowledge (51) the Peruvians that when a cut was made in the outside skin of a rubber tree, a white liquid (...
【简答题】阅读理解。 Thomas Adams discovered bubble gum (泡泡糖) in the 1870s. He was an American. He wanted to find a use for chicle. Chicle is a Spanish word for sticky water that comes from one kind of Mexican tre...