Answer:
C. g(x) = x - 6
Explanation:
For a parent function y = f(x) and n > 0:
f(x) + n : move the graph n units up
f(x) - n : move the graph n units down
f(x + n) : move the graph n units to the left
f(x - n) : move the graph n units to the right
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We have
f(x) = x
Transformation: 6 units down
f(x) - 6 = x - 6