Hello there! Your answer is going to be B. dictionary.
Let's look at the options given.
A. almanac An Almanac provides important dates in the upcoming year and data like tide information, moon cycles, astrology information, etc.
B. dictionary A dictionary gives you a definition for a word or term.
C. encyclopedia An encyclopedia provides information on a certain topic. So, say you want to learn about toads, go to the toads section and there will be a bunch of information on toads.
D. thesaurus A thesaurus gives you synonyms and antonyms for a given word or term.
Now let's look at the question again. It's asking us where we would find the definition for the term valedictory, and look back at what option is. So, to answer your question: a dictionary would be the most helpful tool to find a definition for valedictory.