Correct Answer:
B. would have
Explanation:
The correct answer is would have because this structure represents a third conditional sentence expressing a hypothetical past event.
- Step 1 (Grammatical Structure): The sentence uses an inverted past perfect structure ('Had he worked hard' instead of 'If he had worked hard') to establish a counterfactual past condition.
- Step 2 (Application): Third conditional structures strictly require the main clause to use a modal perfect configuration—specifically 'would have' followed by the past participle verb (V3), which is 'passed' here.
- Incorrect Options:
- will have is incorrect because it is a future perfect marker, which cannot satisfy a counterfactual past conditional requirement.
- would is incorrect because using 'would' alone requires a base verb, not a past participle like 'passed'.
- has is incorrect because it creates a broken present perfect string that fails to indicate a conditional, hypothetical outcome.