Match texts A-D with questions 1-6 below. Some questions match with more than one text. (Nối văn bản A-D với các câu hỏi 1-6 bên dưới. Một số câu hỏi phù hợp với nhiều hơn một văn bản.)
Which invention(s) …
1. was / were discovered during the scientist's free time?
2. was / were made when scientists were working on something else?
3. was / were previously used for something different?
4. resulted from something getting too hot?
5. is / are used for joining two things together?
6. took the longest to be developed?
