The correct answer is B. 50ft
Step-by-step explanation
This image is a contour line in which each line represents a cut of the terrain at a specific height, you can see that the first line has a number zero, the third line has a number 100ft and the sixth line has a number 200ft. Therefore, it can be stated that each line represents an ascent of 50 ft in height because the interval corresponds to 50 ft in height. So, line 1, 0 ft; line 2, 50 ft; line 3, 100 ft; line 4, 150 ft; line 5, 200 ft; and so on. So the correct answer is B. 50ft.