In a specified system, water activity is defined as the ratio of _____

• A. Fugacity of water vapor to fugacity of pure water at the specified system temperature and 1 atmospheric pressure
• B. Fugacity of pure water at the specified system temperature and 1 atmospheric pressure to fugacity of water vapor
• C. Fugacity of pure water at the specified system temperature and 1 atmospheric pressure
• D. Fugacity of water vapor