Highlight the signal words in the paragraph and then answer the question.

Fry remembered a curious adhesive – a strong and yet easily removed “unglue”– that Spencer Silver . . . had come upon several years earlier. . . . Silver felt the unusual adhesive might have some commercial value. . . . 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.

—The Evolution of Useful Things,
Henry Petroski

When did Spencer Silver discover the formula for the “unglue”?

several years before Fry had his idea
the year before Fry had his idea
at the same time Fry had his idea
soon after Fry had his idea

1 answer

The signal words in the paragraph include phrases that indicate time and sequence, such as "several years earlier," "at the time," "had come up with a use for it," and "until the Monday morning when Fry came to work."

Based on the information in the paragraph, Spencer Silver discovered the formula for the “unglue”:

several years before Fry had his idea.