Understanding and application

What is the main function of إِنَّمَا in إِنَّمَا الْأَعْمَالُ بِالنِّيَّاتِ?

Intention, sincere goodwill, and a first nominal sentence (Hadith 1–7)

• A reference to time
• Restriction and emphasis
• A feminine plural marker
• A past-tense form