The $\textsf{TTT}$ diagram for eutectoid steel is shown below. The steel after complete austenitization at $1073 \: \mathrm{K}$ is rapidly cooled to different temperatures and held for varying times (as indicated in $\textbf{Column I}$) followed by quenching to $300 \: \mathrm{K}$. Assuming isothermal transformation, match the heat treatment conditions in $\textbf{Column I}$ with the corresponding microstructure in $\textbf{Column II}$.
$\begin{array}{ll} \textbf{Column I} & \textbf{Column II} \\ (P) \text{Held at } 300 \mathrm{K} \text{ indefinitely} & (1) \text{Bainite} \\ (Q) \text{ Held at } 873 \mathrm{K} \text{ for } 4 \text {minutes} & (2) \text{Martensite} \\ (R) \: \text{Held at } 673 \mathrm{K} \text{ for } 20 \text{ minutes} & (3) \text{Pearlite} \\ (S) \text{Held at } 623 \mathrm{K} \text{ for } 2 \text{ minutes} & (4) \text{Bainite} + \text{Martensite} \end{array}$
- $\mathrm{P}-3 ; \mathrm{Q}-2 ; \mathrm{R}-1 ; \mathrm{S}-4$
- $\mathrm{P}-2 ; \mathrm{Q}-3 ; \mathrm{R}-1 ; \mathrm{S}-4$
- $\mathrm{P}-2 ; \mathrm{Q}-1 ; \mathrm{R}-3 ; \mathrm{S}-4$
- $\mathrm{P}-4 ; \mathrm{Q}-3 ; \mathrm{R}-1 ; \mathrm{S}-2$
