In إِنْ يَصِلْ عَلِيٌّ نَبْدَأْ, which part states the condition?

Conditional Sentences with إِنْ

• نَبْدَأْ
• يَصِلْ عَلِيٌّ
• عَلِيٌّ نَبْدَأْ
• Only عَلِيٌّ