Final answer:
A formal writing style is characterized by proper grammar, avoidance of slang, clear language, and an objective tone. Hence all the above.
Step-by-step explanation:
A formal writing style has several characteristics. Firstly, it requires the use of proper grammar and punctuation to ensure clarity and readability. Secondly, it avoids the use of slang and colloquial language, which can be seen as informal and unprofessional.
Thirdly, a formal writing style is characterized by clear and concise language, with a focus on conveying information efficiently. Lastly, a formal writing style maintains an objective and impersonal tone, meaning that personal opinions and emotions are minimized.