Answer: B. $20$ inches per second

Explanation:1. Understand the concept of rate of change in a linear equation: The given equation $d=20t$ is a linear equation relating distance $d$ and time $t$. It can be written in the form $d = mt + b$, where $m$ is the slope (rate of change) and $b$ is the d-intercept (initial distance). In this case, $d = 20t + 0$. So, the slope $m = 20$ and the d-intercept $b = 0$.

2. Interpret the slope as the rate of change: The slope of the distance-time graph represents the rate of change of distance with respect to time, which is the speed or velocity. Here, the slope is $20$.

3. Determine the units of the rate of change: Distance $d$ is in inches. Time $t$ is in seconds. The rate of change (slope) has units of (units of d) per (units of t), which is inches per second.

4. State the rate of change: The rate of change is $20$ inches per second.

5. Check the solution with the options: Option [B] is "$20$ inches per second", which matches our finding. Option [A] $20t$ is an expression for the distance itself, not the rate of change. Options [C] and [D] represent different rates.

6. Conclusion: The rate of change of the object's distance from its starting position over time is $20$ inches per second.