To answer this question, the user needs to have basic knowledge of building construction and architecture. Vertical connectors between floors can be referred to by different names, depending on the context.

A. Spans: This option is incorrect. Spans refer to the distance between two supports, such as beams or columns, which support a load like a floor or roof.

B. Riser: This option is partially correct. A riser is the vertical component of a step in a staircase that connects one level to another. However, it is not the correct term for vertical connectors in general.

C. Lift: This option is also partially correct. In some parts of the world, "lift" is another term for an elevator, which is a form of vertical transportation. However, it is not a comprehensive term for all types of vertical connectors between floors.

The correct answer is: B. Riser.