Let's match the terms:
- P: Horton equation is used to calculate Infiltration, so P-IV.
- Q: Muskingum method is a method used for Channel routing, so Q-V.
- R: Penman method is used to determine Evapotranspiration, so R-III.
Thus, the correct matching is P-IV, Q-V, R-III, which corresponds to option (A).