At the of a standing wave, there is no displacement from the rest position

The correct answer is "node".

Explanation:

Stationary wave: It is also called standing wave. When two waves of equal frequency or wavelength travelling in opposite direction then  the standing wave will form.

These are those wave which do not appear to move but there is an oscillation up and down in same phase.

Anti node: It is the location in the wave where the amplitude is minimum or there is no displacement from the rest position.

Node: It is the location in the wave where the amplitude is maximum or there is maximum displacement from the rest position.

Therefore, At the node of a standing wave, there is no displacement from the rest position.

your answer is, orbit around the nucleus