If you want the quality of your writings to improve, then avoid redundant words.

The correct answer is D. unnecessary.

A redundant word is a word that

is unnecessary because its meaning is already included in another word or phrase in the sentence. For example, the sentence “I saw it with my own eyes” is redundant because the word “saw” already implies that you used your eyes to see something.

In the sentence “If you want the quality of your writings to improve, then avoid redundant words,” the word “unnecessary” is the only word that is not essential to the meaning of the sentence. The sentence could be rewritten as “If you want the quality of your writings to improve, then avoid using redundant words.”

The other options are all incorrect because they are not redundant words. The word “unwilling” means not wanting to do something. The word “mistaken” means incorrect. The word “wrong” means not correct.

It is important to avoid redundant words in your writing because they can make your writing sound awkward and repetitive. They can also make your writing more difficult to read and understand.