Which construction joint is used to connect two floors?

The choice of a floor-to-floor construction joint is correct because this type of joint specifically addresses the interface and structural connection between two separate floors in a building. Construction joints are vital for managing the expansion and contraction of materials due to temperature changes, as well as accommodating vertical loads and ensuring stability.

In a floor-to-floor joint, the design facilitates proper load transfer between floors while allowing for some movement without causing damage to adjacent structures. This type of joint is essential in multi-story buildings where different floors are subjected to various static and dynamic loads, ensuring structural integrity and safety.

Other options do not accurately represent connections between two floors. For instance, a floor-to-wall joint connects a floor slab to a vertical wall and does not address connections between two horizontal planes. A curtain wall refers to a non-structural exterior wall that does not bear the load of the building, making it irrelevant in the context of connecting floors. Wall-to-wall joints, meanwhile, would pertain to the connection between two walls, which again does not serve the purpose of connecting floors. Thus, floor-to-floor is the most appropriate and effective choice for connecting two floors in construction.