Step 1: Recall the standard instrument/method for each parameter.
- Stream flow velocity is measured with a current meter $\Rightarrow$ A $\to$ IV.
- Evapo-transpiration rate is commonly estimated by Penman's method $\Rightarrow$ B $\to$ II.
- Infiltration rate is evaluated using Horton/Norton-type infiltration methods $\Rightarrow$ C $\to$ III.
- Wind velocity is measured with an anemometer $\Rightarrow$ D $\to$ I.
Step 2: Conclusion.
Thus, the correct matching is A–IV, B–II, C–III, D–I $\Rightarrow$ option (3).


