Where Can the Subtropical Jet Stream Be Located

Where can the subtropical jet stream be located?

A) At any given time, two jet streams exist in each hemisphere.
B) The subtropical jet stream lies over the polar front, an air mass boundary that extends from the Earth's surface upward to the tropopause.
C) The subtropical jet stream forms at the boundary between the high-latitude end of a Hadley cell and the cooler air of mid-latitudes.
D) The subtropical jet stream forms at the boundary of the Ferrel cell and the warmer air of the tropical latitudes.