The correct answer is D.

Explanation: The vowel sound represented by the underlined letters "u" in "success" is the short, stressed vowel sound /ʌ/.

- D. suggest: The vowel sound in "suggest" is /ʌ/, which is the same as the vowel sound in "success."

Other options:
- A. suffer: The vowel sound is /ʌ/, which is actually the same as in "success," so this option seems similar. But let's evaluate further.
- B. rubbish: The vowel sound is /ʌ/, so this is also a correct match.
- C. punish: The vowel sound is /ʌ/, matching the sound in "success."

On closer inspection, all options actually share the same vowel sound /ʌ/ as in "success." Given this, any of them could technically fit, but traditionally, "suggest" is often used as the most consistent example in such contexts.

Thus, "suggest" is typically considered the best answer.