The method of design of flexible pavement as recommended by IRC is A. group index method B. CBR method C. Westergaard method D. Benkelman beam method

The correct answer is: A. group index method

The group index method is a method of design of flexible pavement as recommended by IRC. It is based on the concept of group index, which is a measure of the strength of the subgrade soil. The higher the group index, the stronger the subgrade soil.

The group index method is a simple and easy-to-use method. It is also relatively accurate. However, it is not suitable for all types of subgrade soils.

The other options are incorrect because:

• The CBR method is a method of determining the bearing capacity of subgrade soil. It is not a method of design of flexible pavement.
• The Westergaard method is a method of calculating the stresses and strains in pavements. It is not a method of design of flexible pavement.
• The Benkelman beam method is a method of measuring the deflection of pavements. It is not a method of design of flexible pavement.