A food chain is

a. All the biotic interactions
b. All the feeding relationships in the ecosystem
c. The link between abiotic and biotic factors
D. The single sequence of organisms feeding

TWO examples of abiotic factors needed in an ecosystem are
a. Air and water
b. Food and air
c. Air and plants
d. Food and water

b for the first a for the second sorry if its wrong

Explanation:

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation: