What do close contour lines indicate?

 A series of concentric contour lines that are closed onto themselves indicate mountains or hills. Closed contour lines look like misshapen circles or loops.The lines get closer to each other as the slope gets steeper. If the area has a gentle gradient, the contour lines are more spread out.

Explanation:

if your own plato the answer is b. the fern transitioned from sporophyte generation to gametophyte generation.