In counterfort type retaining walls i) the vertical slab is designed as a continuous slab ii) the heel slab is designed as a continuous slab iii) the vertical slab is designed as a cantilever iv) the heel slab is designed as a cantilever The correct answer is A. (i) and (ii) B. (i) and (iv) C. (ii) and (iii) D. (iii) and (iv)

The correct answer is A. (i) and (ii).

A counterfort retaining wall is a type of retaining wall that uses vertical slabs (counterforts) to support the weight of the soil behind it. The heel slab is a horizontal slab that connects the counterforts and distributes the load of the soil evenly. The vertical slabs and heel slab are both designed as continuous slabs, which means that they are designed to resist bending moments and shear forces.

Option (iii) is incorrect because the vertical slab is not designed as a cantilever. A cantilever is a beam that projects beyond its support and is supported only at one end. The vertical slab in a counterfort retaining wall is supported at both ends by the counterforts and the heel slab.

Option (iv) is incorrect because the heel slab is not designed as a cantilever. The heel slab is supported at both ends by the counterforts.