Which of the following is a prerequisite for forming a mountain wave?

The formation of a mountain wave is primarily dependent on a mountain range of significant height, alongside specific wind conditions. When winds flow over such mountains, they can create disturbances in the airflow, which leads to the development of mountain waves. These waves occur when stable air is forced over the top and down the leeward side of the mountains, creating oscillations in the atmosphere.

The importance of a mountain range of substantial dimension lies in its ability to disrupt the flow of air effectively. If the mountains are not large enough or if the wind conditions are not favorable (such as being perpendicular to the range or having sufficient velocity), the necessary wave patterns will not form. The specific wind conditions must include a flow that is strong enough to overcome the gravitational forces acting on the displaced air, thus enabling the wave phenomena.

Other options, while they may relate to meteorological phenomena, do not encapsulate the specific requirements that lead to mountain wave formation. For instance, the presence of a nearby ocean or wind striking the mountains at acute angles does not address the critical need for a significant mountain range combined with adequate wind dynamics to generate these waves. Similarly, a stable atmosphere can impact how these waves behave rather than focusing solely on their formation prerequisites.