Some of the water quality parameters are measured by titrating a water sample with a titrant. Group I gives a list of parameters and Group-II gives the list of titrants.

$\begin{array}{lll} \text{Group – I} & \text{Group – II} \\ \text{P. Alkalinity} & 1. N/35.5 & Ag NO_3 \\ \text{Q. Hardness} & 2. N/40 & Na_2S_2O_3 \\ \text{R. Chloride} & 3. N/50 & H_2SO_4 \\ \text{S. Dissolved oxygen} & 4. N/50 & EDTA \end{array}$

The correct match of water quality parameters in Group – I with titrants in Group – II is

1. $P – 1, Q – 2, R – 3, S – 4$
2. $P – 3, Q – 4, R – 1, S – 2$
3. $P – 2, Q – 1, R – 4, S – 3$
4. $P – 4, Q – 3, R – 2, S – 1$