Concept:If men and days change but the nature of work remains the same, then workmen×days remains constant.Explanation:Let the required number of days be D.Use the relation: W1M1×D1=W2M2×D2.Here, M1=30, D1=25, W1=15.Also, M2=14, W2=7, and D2=D.Substitute these values:1530×25=714×DSimplify the left side: 15750=50.Simplify the right side: 714D=2D.So, 50=2D.Therefore, D=250=25 days.Answer:14 men will complete 7 projects in 25 days.Correct option: B. 25 days.