ANS:C - risers minus one

The number of treads in a flight of stairs is typically equal to the number of risers plus one. Explanation:

• Treads are the horizontal steps of a staircase, where a person places their feet while ascending or descending.
• Risers are the vertical components that form the face of each step.

To understand why the number of treads is equal to the number of risers plus one, consider the following:

1. Each tread corresponds to the horizontal distance covered by one step.
2. Each riser corresponds to the vertical height between two consecutive treads.

When climbing a staircase, you step onto each tread while ascending. The top surface of the first tread acts as the floor level at the bottom of the flight of stairs. The bottom surface of the last tread is also at the floor level when reaching the top of the flight. Since the top surface of the first tread is at the same level as the bottom surface of the first riser, and the bottom surface of the last tread is at the same level as the top surface of the last riser, the total number of treads equals the total number of risers plus one. So, the correct relationship is: Number of treads = Number of risers + 1.