The answer to this item is most probably letter "C. dictionary". As other options also give information about the word, only the dictionary gives thorough information about it including the way to spell it and pronunciation.
Dictionary is the reference source that would provide the most thorough information about a word, including how to spell the word correctly.
Dictionary is a collection of words in one or more specific languages, often arranged in alphabetical order which may include information on definitions, spelling, pronunciations, etc.
