The rate of infiltration normally declines rapidly during the early part of rainstorm event and reaches a constant value after several hours of rainfall. The factors responsible for this phenomenon are

1. I. the filling of fine soil pores with water, which reduces capillary forces
2. II. moistened soil, clay particles to swell and reduce the size of pores
3. III. raindrop impact breaking up with soil clumps, splashing fine particles into pores

A. I, II

B. I, III

C. II, III

D. All of the above

Answer: Option D