Match the instruments in $Group–I$ with process variable in $Group–2$.

$\begin{array}{cc}\\ &\text{Group-1} & \text{Group-2} \\ &\text{P. Conductivity meter} & \text{ I. Flow} \\ &\text{ Q. Turbine meter} & \text{II. Pressure} \\ &\text{R. Piezoresistivity element} & \text{III. Composition } \\ \\ \end{array}$

1. $P-II$, $Q-I$, $R-III$
2. $P-Il$, $Q-III$, $R-I$
3. $P-III$, $Q-lI$, $R-I$
4. $P-IIl$, $Q-I$, $R-Il$