B because there is no instrument without error however small,

and at all times there will be an estimation error from localisation, an

estimation error of the landmarks and an error in the robot’s controls.

B because even if assuming a perfect ego-estimate of the

robot’s location, there can still be an

A because using a GPS we can precisely estimate the position

of the robot and we know where the robot is located at all times.

Either A or B, depending on the circumstances in the

environment.