Answer:
A. A man of disreputable nature.
Explanation:
Just by looking at the question and answers, you can determine that the most formal statement is "A. A man of disreputable nature." By the use of the word formal, people tend to think of respectful/professional words/things. The words "shady character," and "snake in the grass," are more of a casual/informal way of describing a "suspicious" person.
