Which of the statement about the Polar Front Jet S

单项选择题

Question 17 to 20 are based on the follwing passage. At the end of the passage, you will be given 20 seconds to answer the questions. Now, listen to the passage.

Which of the statement about the Polar Front Jet Stream is INCORRECT

A.It flows around North America and the British Isles.
B.The height it moves ranges from 9 to 13 kilometers above sea level.
C.It is fastest in winter.
D.Its movement has a constant direction.