Which description states a characteristic property of the noble gases? a. relatively unstable b. highly reactive c. colorful and shiny d. very stable

The correct option is D.
Noble gases are very stable, because they have eight electrons in their outermost shells. This is called octet form. Other elements that do not have the octet form try to achieve the form by forming bonds with other elements. Because of their stability, noble gas are chemically inert, that is, they do not undergo chemical reactions with other elements.

The answer is D they are very stable.