Answer:
If I needed to determine how long five score is, the source I would use is:
C) dictionary
Step-by-step explanation:
An atlas wouldn't be helpful in this case since it is a collection of topographic maps, that is, maps that present information related to the physical features of an area. That includes mountains, rivers, plains etc.
A thesaurus presents words accompanied by their synonyms and, sometimes, antonyms. It could help, but only if I didn't have a dictionary.
As we know, dictionaries provide definitions for the words' meanings. If I wish to know what score is, all I need to do is look it up on a dictionary. By the way, score is a name for the number 20. Five score is 5 x 20, which is 100.
An encyclopedia is a group of books providing summarized knowledge about several subjects.