READING COMPREHENSION. READ THE FOLLOWING EXTRACT CAREFULLY AND ANSWER THE QUESTIONS.
In 1970, a man called Spencer Silver was working as a research chemist with the American 3M Corporation. He was working on adhesives and he was asked to create the strongest glue on the market. However, by accident he developed one that could be used on any material without leaving any mark at all. Nobody at 3M showed any interest in that glue until ten years later a colleague of his, Arthur Fry, made use of the adhesive to keep pieces of paper in a book. Sílver´s invention had finally found a use. The surprising thing came when the company he had been working for marketed small blank notes with that glue along one edge. Those notes were called "Post it notes". Nowadays, which office can do without them?