JAMB 1989 · UME · Q28

On the curve shown, the points at which the gradient of the curve is equal to zero are

Worked solution (try it first)

The gradient is zero where the tangent is horizontal, which happens at the turning points: the peaks and the troughs.
The peaks are $b$ , $g$ and $m$ and the troughs are $e$ and $j$ .
So the points are $b, e, g, j, m$ , option B.