Final answer:
The glycol concentration in a cooling tower should not be below 30% to prevent freezing and corrosion, but specific system requirements and recommendations from professionals should be followed.
Step-by-step explanation:
The glycol concentration in a cooling tower should never be lower than a specific percentage to prevent freezing, corrosion, and other issues that might arise due to insufficient glycol presence. While there may be varying recommendations based on the specific system requirements and climatic conditions, option C) 30% is often cited as a standard minimum concentration to maintain the integrity and efficiency of the cooling system. However, before making any changes to the glycol concentration, it is essential to consult the system's manufacturer specifications and a professional to ensure the correct concentration levels for your particular application.