Which highlighted noun is majrur because it follows a preposition?

Introduction to Mansubat and the Ism of Inna

• فِي الْبَيْتِ
• إِنَّ الْبَيْتَ
• الْبَيْتُ وَاسِعٌ
• فَتَحَ حَامِدٌ الْبَيْتَ