Chapter 6 - Differential Equations - 6.1 Exercises - Page 404: 57

matches $(b)$

Given $$\frac{dy}{dx}=\sin(2x)$$ And the figure's below. So, we get at $x=0 \Rightarrow \frac{dy}{dx}=\sin(0)=0 $. This implies that the slope at any point along the $y$-axis is $0$ and that is shown in (b).