Concept:A seam chosen for outer garments must be strong and give a neat finish on both sides.Explanation:A machine felled seam is strong, durable, and lies flat, so it is commonly used on outer garments like shirts, trousers, and jeans.Plain and French seams are not usually chosen for outer garments because they are either less durable or more suited to delicate fabrics.Answer:C. Machine felled seam.