Sentence improvement — correct third conditional: 'If you had attended the meeting, you would have benefited a great deal.' (no change needed).

Given sentence
If you had attended the meeting, you would have benefited a great deal.

Concept/Approach
A third conditional describes an unreal past condition and its past result: If + past perfect → would have + past participle. The tense sequence here is perfect.

Option analysis
Alternatives ('could benefit', 'would benefit', 'benefited') break the correct past counterfactual structure.

Final Answer
No improvement