Celina should use a thesaurus to correct her essay. A thesaurus would provide her with synonyms for the words she used repeatedly, allowing her to replace them with more varied alternatives.
Mike should use a dictionary to correct his essay. A dictionary would provide him with the correct definitions of the words he used in the wrong part of speech, helping him use them accurately in his writing.
Toni should use a dictionary or a vocabulary book to correct her essay. These resources would provide her with the correct definitions of the words she used with unintended meanings, ensuring she uses them correctly in her writing.