Rainfall Intensity and Duration Affect the Likelihood of the Occurrence

Rainfall intensity and duration affect the likelihood of the occurrence of mass movement.Which of the following is true?

A) Rainfall intensity is more important than duration.
B) Rainfall duration is more important than intensity.
C) They are equally important and their effect is universal: a unique combination of rainfall duration and intensity will set off mass movement anywhere.
D) They are both important, but different geologic materials and geographic settings have different resistance to mass movement as started by rainfall.