Question

select the word that means improved something by making small changes. you may have heard that thomas edison invented the light bulb. thats not really true. others had developed bulbs, starting more than seventy years before edison began his work. but edison refined the design of the light bulb in important ways. he was the first to make a light bulb that would last long enough to be practical.

Explanation:

The question asks for a word meaning "improved something by making small changes". From the text, "refined" is used to describe Edison's work on the light bulb design, where he made important small - scale improvements to make it practical. Other words in the text like "invented" or "developed" don't fit the "small changes for improvement" meaning as well as "refined".

Answer:

refined