il reussira_ qu'il reponde a toutes les questions.

The sentence "Il reussira _ qu'il reponde a toutes les questions" requires a conjunction that expresses a condition. The meaning is: "He will succeed provided that he answers all the questions."

The correct conjunction is A condition (followed by que + subjunctive). The construction a condition que introduces a necessary condition for something to happen, and the verb in the subordinate clause takes the subjunctive mood - hence reponde (subjunctive of repondre).

The other options do not fit:

• Bien que means "although" and introduces a concession, not a condition.
• Parce (short for parce que) means "because" and introduces a cause or reason, not a condition.
• Afin (short for afin que) means "in order that" and introduces a purpose, not a condition.

All four conjunctions can govern the subjunctive, but only a condition que expresses the conditional relationship this sentence requires.