Select the most appropriate option that can substitute the highlighted segment in the given sentence. If there is no need to substitute it, select ‘No replacement required’.
If he would have studied harder, he might have passed the exam.

The correct answer is "If he had studied harder".

Step-by-Step Explanation:

1. Identify the conditional structure: The given sentence, "If he would have studied harder, he might have passed the exam," is a third conditional sentence. Third conditional sentences are used to express hypothetical situations in the past that did not happen, along with their imagined past results.

2. Understand the standard rule for Third Conditionals:
The grammatical structure of a third conditional sentence is:
If + Past Perfect (had + past participle), ... would/might/could + have + past participle

3. Analyze the original sentence:
- The "if-clause" uses "would have studied" (incorrect).
- The main clause uses "might have passed" (correct structure for the result clause).

4. Apply the correction:
The verb in the "if-clause" must be in the past perfect tense. The past perfect of the verb "study" is "had studied". Therefore, "would have studied" must be replaced with "had studied".

5. Formulate the correct sentence:
"If he had studied harder, he might have passed the exam." This matches the correct option: "If he had studied harder".