Question

what defines the slope of a roof?
how quickly water runs down it
the rise over the run
when osha requires different fall - protection methods
how steep the roof is

Explanation:

In mathematics, slope is defined as the ratio of the vertical change (rise) to the horizontal change (run). The slope of a roof is also determined by the rise over the run. How quickly water runs down is related to but not the definition, OSHA requirements are about safety and not the definition, and "how steep" is a general description while the rise - over - run is the precise mathematical definition.

Answer:

B. The rise over the run