The correct answer is D. final.
A tentative plan is one that is not yet complete or finalized. It is a preliminary or provisional plan that may be changed or abandoned. An immediate plan, on the other hand, is one that must be carried out without delay. An urgent plan is one that is very important and must be done as soon as possible. A developed plan is one that has been carefully thought out and is ready to be implemented.
The word “final” means “relating to the end or conclusion of something.” It is the opposite of “initial” or “beginning.” In the context of the question, the word “final” is an antonym of the word “tentative” because a final plan is one that is complete and cannot be changed, while a tentative plan is one that is not yet complete and may be changed or abandoned.
The other options are not antonyms of the word “tentative.” A tentative plan may be immediate, urgent, or developed, but it is not necessarily any of those things.