Answer: A) a thesaurus.
Step-by-step explanation: To know which kind of source is better to find information a synonym for the word "contamination", we need to know what is the purpose of every source. A thesaurus is a book that lists words in groups of synonyms and related concepts, a newspaper is a printed publication containing news, feature articles, advertisements, and correspondence, a dictionary is a book that contains the definition of words in alphabetical order, and finally, an encyclopedia is a book or set of books giving information on many subjects or on many aspects of one subject, so the correct answer is option A: a thesaurus.