Explanation:

- Initially, 18 men can complete the work in 20 days.

- Total work can be measured in man-days: 18 men × 20 days = 360 man-days.

- They work for 8 days, completing 18 men × 8 days = 144 man-days.

- Remaining work: 360 - 144 = 216 man-days.

- New deadline is 4 days earlier, i.e., in 16 days total.

- After 8 days, they have only 8 days left to finish the remaining work.

- To complete 216 man-days of work in 8 days, they need 216 ÷ 8 = 27 men total.

- They already have 18 men, so they need 27 - 18 = 9 more men.

Correct Answer: Option 1 - 9