Which phrase correctly applies the idafah exception?

Ghayr Munsarif: Basic Case Pattern and Exceptions

• فِي مَسَاجِدَ اللهِ
• فِي مَسَاجِدُ اللهِ
• فِي مَسَاجِدٌ اللهِ
• فِي مَسَاجِدِ اللهِ