The correct answer is: D. will pass
The sentence “Don’t worry about your exam. I’m sure you will pass” is a statement of encouragement. The speaker is trying to reassure the listener that they are confident that the listener will succeed. The use of the future tense “will pass” indicates that the speaker believes that the listener will pass the exam in the future.
The other options are incorrect because they do not convey the same sense of confidence. Option A, “have passed,” is in the past tense, which indicates that the speaker believes that the listener has already passed the exam. Option B, “pass,” is in the present tense, which indicates that the speaker believes that the listener is currently passing the exam. Option C, “are passing,” is also in the present tense, but it is a progressive verb form, which indicates that the speaker believes that the listener is in the process of passing the exam.
In conclusion, the correct answer is: D. will pass. This option conveys the speaker’s confidence that the listener will succeed on the exam.