Explanation:

In this question, we are given three types of turbines: Kaplan, Francis, and Pelton. We need to determine the specific speeds of these turbines.

Specific Speed:
Specific speed is a parameter used to characterize the shape of a turbine. It is defined as the speed at which a geometrically similar turbine of unit size would run if it were operating under a head of 1m and delivering 1m³/s of water.

Order of Specific Speeds:
The specific speeds of Kaplan, Francis, and Pelton turbines are in decreasing order.

Kaplan Turbine:
The Kaplan turbine is a propeller-type water turbine. It has a higher specific speed compared to the other two turbines. Kaplan turbines are designed to operate efficiently under low head and high flow conditions. They have adjustable blades that allow them to operate over a wide range of flow rates. Hence, the specific speed of Kaplan turbines is the highest among the three.

Francis Turbine:
The Francis turbine is a reaction turbine. It has a medium specific speed. Francis turbines are designed to operate efficiently under medium head and flow conditions. They have fixed blades that do not allow for as much adjustment as the Kaplan turbines. Hence, the specific speed of Francis turbines is lower than Kaplan turbines but higher than Pelton turbines.

Pelton Turbine:
The Pelton turbine is an impulse turbine. It has the lowest specific speed among the three. Pelton turbines are designed to operate efficiently under high head and low flow conditions. They have buckets or cups that capture the kinetic energy of the water jet.

Conclusion:
Based on the characteristics and design of the three turbines, the specific speeds of Kaplan, Francis, and Pelton turbines are in decreasing order. Hence, the correct answer is option 'B' - the decreasing order.