Introduction:
A regenerator is a type of heat exchanger used in gas turbine systems to improve efficiency. It works by preheating the air before it enters the combustion chamber, reducing the amount of heat energy required to be supplied to the system. This, in turn, improves the overall efficiency of the gas turbine.

Explanation:
Using a regenerator in a gas turbine system offers several advantages that contribute to its improved efficiency. The correct answer to the question is option 'B', which states that the heat required to be supplied is reduced. Let's explore this in more detail:

1. Preheating the air:
A regenerator functions by transferring heat from the hot exhaust gases leaving the turbine to the cooler air entering the combustion chamber. The regenerator consists of a matrix of heat-absorbing material through which the exhaust gases flow, transferring their heat energy to the matrix. When the air passes through the regenerator, it absorbs this preheated energy, reducing the amount of heat that needs to be supplied during the combustion process.

2. Reducing fuel consumption:
By preheating the air using a regenerator, the temperature of the air entering the combustion chamber is increased. This higher temperature allows for more efficient combustion, reducing the fuel consumption required to achieve the desired power output. As a result, less heat energy needs to be supplied to the system, leading to improved efficiency.

3. Utilizing waste heat:
Gas turbines produce high-temperature exhaust gases as a byproduct of the combustion process. Without a regenerator, this waste heat is simply expelled into the environment. However, by using a regenerator, the waste heat is captured and reused to preheat the air, effectively utilizing this otherwise wasted energy. This reuse of waste heat further reduces the heat energy that needs to be supplied to the system.

4. Improved thermodynamic cycle:
The addition of a regenerator to a gas turbine system modifies the thermodynamic cycle, resulting in improved efficiency. The regenerator effectively increases the specific heat capacity of the air, allowing for more heat to be transferred during the combustion process. This increased heat transfer contributes to a higher overall efficiency of the system.

Conclusion:
In conclusion, the efficiency of a single gas turbine can be improved by using a regenerator because it reduces the heat required to be supplied to the system. By preheating the air and utilizing waste heat, the regenerator enhances the combustion process and reduces fuel consumption, ultimately leading to improved efficiency.