Screening performance: choose the correct statement about capacity versus effectiveness and the construction of a reel (revolving screen) used in flour mills.

Introduction / Context:
Screen selection involves trade-offs between throughput (capacity) and separation quality (effectiveness). In addition, certain industries use specialized screen constructions tailored to their products, such as reels in flour milling.

Given Data / Assumptions:

• Capacity means tons/hour passed; effectiveness means separation accuracy (sharpness of cut, undersize in oversize, etc.).
• Flour-mill reels are cylindrical, slowly rotating screens.

Concept / Approach:
As feed rate increases, bulk bed depth and blinding generally worsen, reducing screening effectiveness. Thus capacity and effectiveness oppose each other beyond a certain point. In flour mills, "bolting cloth" (silk or synthetic) is stretched over supporting wire mesh to form the reel’s screening surface, providing fine apertures with structural support.

Step-by-Step Solution:
Acknowledge the trade-off: higher capacity often reduces effectiveness.Recall construction: silk bolting cloth over wire mesh in reels.Therefore, statements (b) and (c) are correct.

Verification / Alternative check:
Performance curves for screens show decline in efficiency with excessive loading; flour milling texts detail reel construction with bolting cloth.

Why Other Options Are Wrong:
(a) Equating capacity to effectiveness is incorrect; they are distinct and often competing objectives.

Common Pitfalls:
Attempting to maximize both simultaneously without considering bed depth limits and screen blinding control.

Final Answer:
both (b) and (c).