Step 1: Understanding the Concept:
This question asks to identify a type of windmill that possesses a specific combination of characteristics: good power coefficient (efficiency), high starting torque, and low cost. We need to evaluate each windmill type based on these criteria.
Step 2: Detailed Explanation:
Let's analyze the characteristics of each windmill type:
(A) Horizontal axis single blade type: This design (along with two-blade designs) can operate at very high speeds and can have a good power coefficient, but they have very low starting torque. They are also complex to balance and are not low cost. They are not common.
(B) Horizontal axis multibladed type: This is the classic "American farm windmill" design, with many blades (typically 12-24).
Starting Torque: Because of the large number of blades and their high solidity (the fraction of the swept area covered by blades), this type has a very high starting torque. This makes it excellent for its traditional application: pumping water, which requires a lot of force to start.
Power Coefficient: It operates at a low tip-speed ratio and has a moderate or "good" power coefficient for its intended purpose (though lower than modern high-speed turbines).
Cost: It is a relatively simple, robust design that has been manufactured for over a century, making it a low-cost and reliable option for mechanical work like water pumping.
(C) Sail type: This is an ancient design (like traditional Dutch windmills). They have high starting torque but are structurally massive, have a lower power coefficient compared to modern designs, and are not considered low cost in a modern context.
(D) Darrieus type: This is a Vertical Axis Wind Turbine (VAWT) with an "eggbeater" shape. It has a good power coefficient at high speeds but has a notoriously low (often zero or negative) starting torque, meaning it often needs an external motor to get started.
Step 3: Final Answer:
The horizontal axis multibladed windmill is the best fit for all three criteria: good power coefficient for its class, high starting torque, and low cost. Therefore, option (B) is correct. The correct option is actually missing from the OCR, I will assume it's option 2 or 3 and it matches the description. Based on the description, "Horizontal axis multibladed type" is the answer. Let's assume option 2 is "Horizontal axis multibladed type".
{Note: The provided solution appears to have a checkmark on option 2, but the text for option 2 is not fully captured in the OCR. Assuming option 2 is the multibladed type based on standard knowledge.}