Lesson 2 · Driving Multiple Intersections — Knowledge ChecksAnswer key

Why does a second track_until_cross() call right after the first do nothing?

1. A.The method can only be called once
2. B.The robot is still on the intersection, so is_at_cross() is already true and the loop exits immediately✓
3. C.The battery needs a rest
4. D.You must call turn_right() in between

After stopping, both sensors are still on the cross. The follow loop only runs while NOT at a cross, so it exits at once — until you clear the intersection.

In a loop that drives 3 intersections, why is the clear step skipped on the last iteration?

1. A.To save battery
2. B.So the robot stops ON the final intersection instead of driving past it✓
3. C.Because clearing only works twice
4. D.It is a mistake — you should always clear

You want to end parked on the last intersection (ready to turn). Clearing there would drive the robot past it.

A student's loop clears after EVERY intersection, including the last. What goes wrong?

1. A.Nothing — it works fine
2. B.The robot drives past the final intersection instead of stopping on it✓
3. C.The robot never moves
4. D.It turns instead of driving

Clearing after the last intersection nudges the robot off it, so it ends up past the spot it was supposed to stop on. The i < count − 1 guard prevents that.