How does the actual exam difficulty compare to the speaker's expectations?

The speaker’s experience with the exam suggests that it turned out to be easier than anticipated. This aligns with the choice that indicates the exam was not as bad as expected, indicating a sense of relief or pleasantly surprising results compared to fears or concerns leading up to the examination. This reflects a common sentiment where individuals may prepare for a challenging experience, but find that the reality is more manageable.

In contrast, the other options suggest a range of negative outcomes. For example, stating the exam was tougher or far worse than expected emphasizes an experience that was more strenuous or disappointing than what the speaker had hoped for. Saying it was as difficult as assumed implies that the speaker's expectations were met without any deviation, which doesn’t capture the contrast between expectation and reality that choice D highlights. Thus, the correct answer provides an optimistic perspective on the outcome, contrasting the more negative or neutral sentiments expressed in the other choices.