The answer to your question would be that the element that is necessary to complete the sentence above is the following one: Subject. That is, the correct option would be D.
A sentence is a group of words giving a complete thought. What is more, a sentence must contain a subject and a verb. In this case, the sentence does have a verbal predicate but no subject. Therefore, this sentence is grammatically incorrect.
D) Subject is the element necessary to complete the sentence above. You already have a predicate (drives), so you don't need that, or a subordinate/independent clause. What you do need is a subject. For example: <em>Mercedes </em>drives like no other car.
