Concept:This is a sentence rearrangement question that tests logical flow and grammatical correctness.
Explanation:The sentence starts with a time reference.
Part S ("twenty years from now") gives the time context and opens the sentence correctly.
Next, part P ("you will be more disappointed") naturally follows, stating the main feeling.
The phrase "more disappointed" needs a comparison.
Part R ("by the things you didn't do") introduces the first item compared.
Finally, part Q ("than by the ones you did do") completes the comparison using "than".
Thus the correct sequence is S, P, R, Q.
Compare with the options: Option D (SPRQ) matches this order.
Answer:Option D (SPRQ)