I think unplugging DVD players
The reason why it is considered courageous for the musicians to play
"under the open sky" is because they are facing a dangerous situation.
<h3>What is Courage?</h3>
This refers to the quality that means that there is the strength to face fear and do the right thing.
Hence, it is important to note that for someone to display courage, then that means that they are facing threats or fear and need to overcome it.
Please note that your question is incomplete so I gave you a general overview to help you get a better understanding of the concept.
Read more about courage here:
brainly.com/question/26489684
It helped with faster transportation.
Density (a) is the correct answer
<span>Scientists believe that differences in density cause hot, plastic-like rock in the asthenosphere to rise toward earth's surface. </span>