The correct answer is: A. poles
The jet stream is a fast-flowing, narrow air current found in the upper atmosphere. It flows from west to east, and its position varies with the seasons. In the winter, the jet stream is located further south than in the summer. The jet stream is strongest at the poles and weakest at the equator.
The troughs of the waves are where the jet stream is closest to the poles. This is because the jet stream is strongest at the poles and weakest at the equator. The troughs of the waves are also where the jet stream is most variable. This is because the jet stream is affected by the Earth’s rotation and the Earth’s surface temperature.
The other options are incorrect because the jet stream is not closest to the equator, the Prime meridian, or any other location on the Earth’s surface.
The jet stream is a powerful weather phenomenon that can have a significant impact on the Earth’s climate. It is important to understand the jet stream in order to predict weather patterns and climate change.