D) a depression
This
is a common topographic symbol for a depression:
Refer
to the map below for other features on the map example used in Nature IQ,
explanations are below the map.
Drawn
Contour Lines
- Steep slopes - contours are closely spaced
- Gentle slopes
- contours are less closely spaced
- Valleys - contours form a V-shape pointing up the hill -
these V's are always an indication of a drainage path which could also be a
stream or river.
- Ridges - contours form a V-shape pointing down the hill
- Summits - contours forming circles
- Depressions - are indicated by circular contour with lines
radiating to the center
Source: http://www.princeton.edu/~oa/manual/mapcompass.shtml