Which action will not allow the robot to move accurately in a straight line?

When a robot is required to move accurately in a straight line, it is crucial that the motors on either side of the robot are synchronized to maintain a uniform direction and speed. Activating opposing motors at different speeds introduces a discrepancy in power delivery to each side of the robot, causing it to veer off course instead of going straight.

In contrast, using only one motor will result in the robot being unable to move at all or possibly pivot in place, rather than moving straight. Activating both motors with equal power ensures that they are working in tandem, providing balanced propulsion that drives the robot forward in a straight line. Similarly, using a constant speed on both motors also contributes to this straight-line movement, as both motors will be contributing to the same direction at the same rate.

Hence, the action that will not allow the robot to move accurately in a straight line is the one where opposing motors are activated at different speeds, as it inherently creates an imbalance that leads to deviation.