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 modify nouns. In the sentence, "groundbreaking" modifies "work", "thin" modifies "threads", and "fiber - optic" modifies "cables".

Answer:

groundbreaking, thin, fiber - optic