Jet planes can fly very easily and smoothly in the lower part of the stratosphere. What is the appropriate explanation for this? 1. There are no clouds or water vapor in the lower part of the stratosphere. 2. There are no vertical winds in the lower part of the stratosphere. In this context, which of the above statement(s) is/are the appropriate explanation(s) for this?

• A. only 1
• B. only 2
• C. 1 and 2
• D. neither a nor 2