A jet stream is a belt of wind in the upper atmosphere that blows around the Earth from west to east.

How is the jet stream related to the wind direction on the ground?
A.
When the jet stream moves south, it moves its associated weather front, which causes winds from the north.
B.
When the jet stream blows from the west, the wind on the ground blows from the west.
C.
It can slow down or speed up, causing wind on the ground to blow north or south.
D.
It can move air from the upper atmosphere to the lower atmosphere to bring circular winds.