The correct answer is A) Essential idioms in English
Explanation:
Formal writing involves writing about academic subjects or serious issues by using an objective tone and avoiding the use of colloquial language, which includes idioms, slangs, and similar. Due to this, when you are writing a formal text and you have any questions related to this, reading a source related to idioms is never the way to find the answer to your question. Indeed, using idioms is never recommended in formal writing, and therefore knowing how to use them is useless for formal texts. Instead, you should look for manuals of styles such as the MLA Handbook or the Chicago manual as these focus on formal writing.
