Which of the following best describes a vocabulary system called word forms?

a. examine the roots, prefixes, and suffixes of words to make an educated guess as the the word's meaning.
b. learn how a root word changes when used as a noun, verb, adjective, or adverb to learn multiple related words at the same time.
c. learn the history of the changing forms of a word to identify its meaning.
d. none of the above