With respect to metal working, match Group A with Group B: Group A P. Defect in extrusion Q. Defect in rolling R. Product of skew rolling S. Product of rolling through cluster mill Group B I. alligatoring II. scab III.fish tail IV. seamless tube V. thin sheet with tight tolerance VI. semi-finished balls of ball bearing

• A. P-II, Q-III, R-VI, S-V
• B. P-III, Q-I, R-VI, S-V
• C. P-III, Q-I, R-IV, S-VI
• D. P-I, Q-II, R-V, S-VI