Final answer:
The coefficient of variation (CV) for the control is approximately 4.38%.
Step-by-step explanation:
To calculate the coefficient of variation (CV), divide the standard deviation (2SD) by the mean (M) and multiply by 100. In this case, the standard deviation is 6 mg/dL and the mean is 137 mg/dL. So, the CV = (6/137) x 100 ≈ 4.38%. Therefore, option c) 4.38% is the correct answer.