Which phrase correctly uses the place word as mudaf?

Maf'ul Fih: Adverbs of Place

• تَحْتٌ الشَّجَرَةِ
• تَحْتًا الشَّجَرَةِ
• تَحْتِ الشَّجَرَةُ
• تَحْتَ الشَّجَرَةِ