An adverb is a word or phrase that qualifies or changes an adjective, verb or another adverb, to express a relation of a situation, cause etc.
The correct answer is A)NO CHANGE as the adverb is positioned correctly in the given sentence.
Options B, C, and D are wrong as the sentence structure is wrong, the object is not positioned correctly, and the adverb is not positioned correctly.
He is writing the letter carefully.