Answer
C
Work Step by Step
The slope of the tangent line through the point on the graph of $f$ where $x=a$ is given by the instantaneous rate of change, or derivative
$m_{tan}=$ slope of tangent $=$ instantaneous rate of change$=$derivative $=f^{\prime}(a)$
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Reading the graph, (0, 0.7) seems to be on the graph.
So, $f(4)\approx 0.7$ (which eliminates choices A and B)
The tangent line (sketch it) at (4,0.7) seems to be parallel with the line y=x, which has slope 1 ( rises by 1 when x changes by 1).
so
we select choice C
