अंदर की ओर उच्च मानों वाली बंद समोच्च रेखाएं (closed contour lines) किसे दर्शाती हैं?

Consider the following statements about the characteristics of contours: I. Closed contour lines with higher values inside show a depression/lake. II. A contour is an imaginary line joining points of equal elevation. III. Closely spaced contours indicate a steep slope. IV. Contour lines can cross each other in the case of an overhanging cliff. Which of these statements are correct?

At what angle does a contour line cross a ridge line or a valley line?