Correct the ending in the basic phrase فِي مَسَاجِدِ when the noun has neither al nor idafah.

Ghayr Munsarif: Basic Case Pattern and Exceptions

• فِي مَسَاجِدَ
• فِي مَسَاجِدٌ
• فِي مَسَاجِدٍ
• فِي مَسَاجِدُ