Option C: 40 m
Using tan 45° = 1, the horizontal distance from observer's eyes to chimney = 38.2 m. So the chimney height above eye level = 38.2 m. Total height = 38.2 + 1.8 = 40 m.
This follows the same method as Example 3 in the textbook. The observer's eye level is 1.8 m above the ground. Since tan 45° = 1, the vertical rise from eye level equals the horizontal distance (38.2 m). Add the observer's height (1.8 m) to get the total chimney height: 38.2 + 1.8 = 40 m. Always remember to add the observer's height to the calculated vertical distance to get the height above ground.