Answer:
C. -7x
Explanation:
Only one of the offered choices passes the horizontal line test: at most one point of intersection with any horizontal line.
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A: a parabola opening upward, so will have two points of intersection with a general horizontal line (only one at the vertex).
B: a horizontal line, so will have an infinite number of points of intersection with a horizontal line.
D. A "V-shaped" graph that will generally have two points of intersection with a horizontal line (only one at the vertex).