A possible slope failure is shown in the figure. Three soil samples are taken from different locations $\text{(I, II}$ and $\text{III)}$ of the potential failure plane. Which is the most appropriate shear strength test for each of the sample to identify the failure mechanism? Identify the correct combination from the following options:
- Triaxial compression test
- Triaxial extension test
- Direct shear or shear box test
- Vane shear test
- $\text{I-Q, II-R, III-P}$
- $\text{I-R, II-P, III-Q}$
- $\text{I-S, II-Q, III-R}$
- $\text{I-P, II-R, III-Q}$