The correct option is B suddenly
The underlined word "sudden" is an adjective that usually modifies a noun that is abstract or an object, not a person, the word needs to be changed. Hence option D is not correct. Option A is correct because it describes the manner in which the man appeared (adverb of manner), i.e., in an abrupt way. Option B is incorrect because the word does not exist in the English language. Option C is a comparative, which is used when a comparison is made between two nouns or phrases. The given sentence does not contain any phrase or noun with which the 'man' can be compared, hence option C is incorrect.