The question asks to identify which graph models walking directly away from a motion sensor at a constant rate. Let’s analyze each graph:

• Graph a: The distance $d$ remains constant over time $t$, indicating no movement. This would not represent walking away or towards the sensor.

• Graph b: The distance $d$ decreases linearly with time $t$, indicating movement towards the sensor at a constant rate, but not away from it.

• Graph c: The distance $d$ increases linearly with time $t$, which indicates walking away from the sensor at a constant rate. This is the correct graph.

• Graph d: The distance $d$ increases, but at a decreasing rate (curved graph), suggesting an acceleration or deceleration, which doesn't fit the description of a constant rate.

Thus, the correct answer is C.

Would you like more details on any of these graphs? Here are five related questions:

1. What does a graph look like if someone is walking towards the sensor at a constant rate?
2. How would the graph look if the person is walking away from the sensor at a non-constant rate?
3. Can you explain what kind of motion Graph D might represent?
4. How would a graph change if the person started walking, stopped, then started again?
5. Why does Graph A not represent any motion?

Tip: A straight line (linear relationship) on a distance-time graph indicates constant speed.