Topic: Conditional Sentence,

Best Answer Explained in Below-:

The sentence "He – arrested if he had tried to leave the country." implies a conditional situation relating to the past. To understand why "would have been" is the correct choice, we must look at the structure of conditional sentences, particularly the third conditional, which expresses hypothetical situations that did not happen in the past.

In this case, the phrase suggests a cause and effect that hinges on a past action (trying to leave the country) that did not occur. The structure of a third conditional sentence typically follows the format: "If + past perfect, would have + past participle." Therefore, the correct completion of the sentence must maintain this grammatical structure.

Option C, "would have been," correctly fits this structure because it implies that had he attempted to leave (a past condition that didn’t happen), the result would have been that he was arrested. This reflects a regrettable or hypothetical outcome based on that non-action.

The other options do not fit grammatically:
- Option A ("would") lacks the necessary past conditional structure.
- Option B ("could be") suggests possibility in the present or future, not the past.
- Option D ("must be") implies certainty, which deviates from the hypothetical meaning.

Hence, "would have been" is the only option that accurately reflects the intended conditional meaning of the sentence.