7. Why is the development of a battery system essential for the effective use of wind power?
a. Windmills require batteries to turn them.
Ob. Batteries supply power for transporting
electricity from one place to another.
O c. Batteries store excess power for use when the
wind does not blow.
d. Battery farms use less land than wind farms
commonly do.

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:

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the correct answer would be d. hope this !