Step 1: Group Index (GI) Method.
This empirical method is based on soil classification properties. Thus, A corresponds to III.
Step 2: CBR Method.
The California Bearing Ratio (CBR) method is an empirical technique that utilizes soil strength tests. Accordingly, B corresponds to IV.
Step 3: US Navy Method.
This method employs a semi-theoretical approach. Therefore, C corresponds to I.
Step 4: Asphalt Institute Method.
This method is quasi-rational, integrating theoretical and experimental methodologies. Consequently, D corresponds to II.
Step 5: Conclusion.
The correct pairings are A - III, B - IV, C - I, and D - II. The correct selection is (C).
The recommended minimum traffic growth rate and design period considered for structural design of flexible pavements for national highways in India as per IRC 37:2018 is __________ percentage and _________ years, respectively.