Writers can improve their writing by focusing on one writing skill at a time. The answer is option C. The fourth skill that we have to learn is writing. But writing is not just about putting our thoughts into written words. Writing also needs a set of skills to learn and improve. Basically, it includes proper use of words and correct choice of words, punctuation marks, and even spelling. Also, how to correctly arrange and format sentences matter. Inappropriate application of the basics makes writing useless because the message you are trying to convey is not understandable.