Which of the following statement about Stratosphere is / are true

• A. Extends out to about 50 km (30 miles)
• B. The bottom of this layer is calm. Jet planes often fly in the lower Stratosphere to avoid bad weather in the Troposphere
• C. The upper part of the Stratosphere holds the high winds known as the jet streams. These blow horizontally at speeds up to 480 km / hour (300 miles / hour)
• D. All of the above