A road is divided into four sections having varying widths as shown in the figure. Section-$2$ (S$2$) represents a capacity constrained condition with respect to the traffic flow passing through Section-$1$ (S$1$). Section-$3$ (S$3$) and Section-$4$ (S$4$) do not face any such capacity constraint with respect to the flow. A flow-density relationship for unconstrained and constrained flow conditions is shown in the figure.
If Section-$1$ observes density D$2$, the option representing the correct state of density in Sections $2, 3$ and $4$ is:
- $\mathrm{S} 2-\mathrm{D} 4 ; \mathrm{S} 3-\mathrm{D} 3 ; \mathrm{S} 4-\mathrm{D} 2$
- $\mathrm{S} 2-\mathrm{D} 3 ; \mathrm{S} 3-\mathrm{D} 2 ; \mathrm{S} 4-\mathrm{D} 1$
- $\mathrm{S} 2-\mathrm{D} 3 ; \mathrm{S} 3-\mathrm{D} 4 ; \mathrm{S} 4-\mathrm{D} 2$
- $\mathrm{S} 2-\mathrm{D} 4 ; \mathrm{S} 3-\mathrm{D} 3 ; \mathrm{S} 4-\mathrm{D} 1$
