Right choice is (c) Smaller overall thickness in monolithical construction
Easiest explanation: In cement concrete flooring, non-monolithical construction is preferred over monolithical construction because of the following disadvantages of monolithical construction. These are the development of hair cracks, damaging of the topping and slow work progress in monolithical construction. However, the only advantage of monolithical construction is that in this, good bonds are formed which result in smaller overall thickness.