The correct answer is B- It can teach the meaning of words and their roots.
Explanation:
Regular dictionaries list the words of a language along with information of them especially information related to the meaning or meanings of each word and additional information related to their origin, root, pronunciation, and type of word. Due to this, by using a dictionary you can learn about the precise meaning/s of each word and their roots which would help you to use more precise words while writing. According to this, the main way a dictionary can help you to improve your writing is that "it can teach the meaning of words and their roots".
