The answer to this is A. You need to go to tools then choose word count. This can be very effective as it will let you know how many words you have used up so far. This can be crucial when you need to submit a 500-word article. If the article does not reach 500 words, then you need to find more information that will allow you to reach that number.
After reaching the required number of words, that is the time when you can check out the different statistics of the document. For example, you may want to check the spelling and grammar of your document. There is a spell check feature that you can easily use.
Although the simple answer is to display word count, found under Tools on a word processor, what you might display depends upon the reason and function of the document. Word count is most useful if for publication - newspapers and journals will want a precise length. It may also be that for university study a set length has been prescribed and displaying word count provides evidence that this has been adhered to.
However, if the document is an article for students of the language, then displaying spelling and grammar might be an appropriate guide, or illustration of relevant learning.
You receive numerous statistics on your document (including word count, ease of reading, and grade level) when you use spelling and grammar check! For displaying the documents about any document, I would prefer to use Tools and word count.