Final answer:
A decrease in skin folds and an increase in girth measurements typically imply increased muscle mass as it suggests a reduction in fat mass and an enlargement of muscle size.
Step-by-step explanation:
When combining skin fold and girth measurements, a decrease in skin folds and an increase in girth measurements would most likely imply increased muscle mass (c). Skin fold measurements are used to estimate body fatness by measuring the thickness of the fat layer under the skin using a tool known as calipers. If skin folds decrease, it suggests that there has been a reduction in fat mass. On the other hand, girth measurements involve measuring the circumference of different body parts. An increase in girth, especially when accompanied by reduced skinfold thickness, often indicates that muscle size has increased since muscle is denser and takes up less space than fat for the same amount of weight.