Sentence 1: I bought a 1969 Mercury Montego with a loose front seat. 
 Sentence 3: I removed the seat and repaired the floor with pieces of sheet metal 
 Sentence 4:  My repair held the seat firmly in place after I reinstalled it 
 Sentence 5:  The car then successfully passed the safety inspection 
 Option 1: The seat was loose because the car's floor had rusted through. 
 Option 2: I had to pay someone to repair the rusted floor, which caused the loose seat.