The correct option is A Expansion
The gaps are left between concrete roads to accomodate for the expansion of concrete as the temperature changes. Without it, cracks form in the concrete which makes it weak. Tar is a water proofing material and a good filler as it has flexibility. This way concrete can expand between the joint and when it contracts, tar will make up for the open joint space.Hence, Option A is correct. The rest of the options do not express this condition, hence, incorrect.