Which of the following is not correct with respect to Jet Streams?

• A.  Jet streams are strong winds with normal speed of 100 to 300 km/hr
• B.  Discovery of the Jet Streams was made by American airplanes during the World War I
• C.  Jet streams shift pole wards during summer and equator wards during winter season.
• D.  Velocity of the Jet stream in winter is almost twice the velocity the summer.