Lesson 2 · Drive to the Edge and Stop — Knowledge ChecksAnswer key

Which loop fits the task 'drive until the robot detects a line'?

1. A.A for loop — you know it takes exactly 4 steps
2. B.A while loop — you repeat until a condition changes, however long that takes✓
3. C.Neither — you cannot loop with sensors
4. D.Both work exactly the same here

You don't know the number of steps in advance, so you loop while the sensor says 'no line' — that's a while loop.

A student's robot drives forward and never stops, even over the line. What did they most likely forget?

1. A.The board.wait_for_button() line
2. B.To re-read the sensor inside the loop, so the condition never changes✓
3. C.To import the drivetrain
4. D.To charge the battery

Without updating left inside the loop, the condition stays true forever — a classic infinite loop.

The threshold is 0.5 and the sensor reads 0.3. Is `left < threshold` True or False?

1. A.True — 0.3 is less than 0.5✓
2. B.False — 0.3 is greater than 0.5
3. C.True — they are equal
4. D.It causes an error

0.3 < 0.5 is True, so the loop keeps running — the robot is still on white and should keep driving.