The correct answer is C) Reduced fuel consumption. The build-up of contamination in a gas turbine will cause increased combustion gas temperatures, restricted airflow, and turbine blade corrosion, but it will not lead to reduced fuel consumption. In fact, the opposite is true - the contamination will cause the gas turbine to be less efficient, requiring more fuel to produce the same power output. The other answer choices (A, B, and D) are all correct consequences of contamination build-up in a gas turbine, as they impair the engine's performance and efficiency. However, the increased fuel required to maintain power output is the key factor that distinguishes this question.