The correct answer is D. You should have studied for your exams.
The simple future tense is used to talk about things that will happen in the future. It is formed with the verb “will” or “shall” plus the base form of the verb.
In option A, “Shall I open the window?”, the verb “shall” is used to make a polite request. It is not in the simple future tense.
In option B, “You will do exactly as John says”, the verb “will” is used to make a command. It is in the simple future tense.
In option C, “He’ll carry your luggage for you”, the verb “will” is used to make a prediction. It is in the simple future tense.
In option D, “You should have studied for your exams”, the verb “should” is used to express regret or disapproval. It is not in the simple future tense.