Explanation:
Original sentence:
"The plaintiff made very cogent submissions to the trial judge."

The plaintiff is the person who brings a case to court — the one making a complaint or initiating a lawsuit.

Looking for the opposite:
The opposite of the plaintiff in a legal case is the person who is being sued or accused — that is, the defendant.

let's evaluate the options:
A. bailiff – An officer of the court, not a party in the case.
Incorrect

B. prosecutor – A lawyer who brings a criminal case on behalf of the state. Not the direct opposite of plaintiff in general.
Incorrect

C. lawyer – A legal professional. Could represent either side, not the opposite of plaintiff.
Incorrect

D. defendant – The person who responds to the plaintiff’s claim; the opposite party in a civil case.
Correct

E. accused – This applies more specifically to criminal cases, not civil ones.
Incorrect