Question

select the three adjectives. dont select any articles (a, an, or the). charles kuen kao won the nobel prize in physics in 2009 for groundbreaking work on fiber - optic cables, which use thin threads of glass or plastic to carry information in the form of light.

Explanation:

Adjectives describe nouns. In the text, "groundbreaking" describes the work, "thin" describes the threads, and "fiber - optic" describes the cables.

Answer:

groundbreaking, thin, fiber - optic