In late 1997, the chambers inside the pyramid of the Pharaoh Menkaure at Giza were closed to visitors for cleaning and repair due to moisture exhaled by tourists, which raised its humidity to such levels so that salt from the stone was crystallizing and fungus was growing on the walls.

• Adue to moisture exhaled by tourists, which raised its humidity to such levels so that salt from the stone was crystallizing  
• Bdue to moisture that tourists had exhaled, thereby raising its humidity to such levels that salt from the stone would crystallize  
• Cbecause tourists were exhaling moisture, which had raised the humidity within them to levels such that salt from the stone would crystallize  
• Dbecause of moisture that was exhaled by tourists raising the humidity within them to levels so high as to make the salt from the stone crystallize  
• Ebecause moisture exhaled by tourists had raised the humidity within them to such levels that salt from the stone was crystallizing