Question

fry remembered a curious adhesive – a strong and yet easily removed \unglue\– that spencer silver, another 3m researcher, had come upon several years earlier. . . . silver felt the unusual adhesive might have some commercial value, and so he demonstrated it to various colleagues, including fry. at the time, no one had come up with a use for it, and so the formula for the weak adhesive was filed away – until the monday morning when fry came to work with the idea of making sticky bookmarks that could also be removed without damaging the book.
—the evolution of useful things,
henry petroski
why was spencer silver’s work an essential part of fry’s invention?
○ he worked alongside fry on the sticky notes.
○ he convinced other people to believe in fry’s invention.
○ he told fry about the \unglue\ that he had discovered.
○ he came up with a commercial use for the \unglue.\

Explanation:

El texto dice que Fry recordó un adhesivo que Spencer Silver había descubierto años antes. Silver demostró este adhesivo a varios colegas, incluyendo a Fry. No se usó en ese momento, pero cuando Fry tuvo la idea de hacer marcas de libros adhesivas, ese adhesivo fue esencial. Las otras opciones no son correctas: no se dice que Silver trabajara junto a Fry (primera opción), ni que convirtiera a otras personas (segunda opción), y la cuarta opción dice que Silver tuvo un uso comercial, pero el texto dice que fue Fry quien tuvo la idea del uso (hacer marcas de libros).

Answer:

He told Fry about the "unglue" that he had discovered.