Which of the following is a rule for PCB layout?

The choice indicating that tracks must not touch additional pads or tracks is essential in PCB layout to prevent short circuits and ensure proper functioning. When conducting electricity, the proximity of conductive paths can lead to unintended connections, leading to faults in the circuit. This rule helps maintain signal integrity and reliability in the performance of the printed circuit board.

The other potential options contribute to poor design practices. For instance, arbitrary thickness of tracks may compromise the current capacity and mechanical stability of the PCB. Placing components randomly can create routing issues and make the board difficult to manufacture, test, and repair. Having all tracks of equal length is impractical as it does not consider factors such as the need for differential signaling or timing delays in high-frequency applications. Proper adherence to layout rules is crucial in achieving an efficient and functional circuit design.