The options to choose from are:
A. The music is upbeat and includes singing.
B. They're sitting up straight in a chair that minimize dozing.
C. The music is enjoyable rather that agitating.
D. Electronic devices are nearby so that important communications are received.
The correct answer is C. If you are using music as a means to relax you need to make sure that you are listening to something that is enjoyable and is calming your mood, so not something that could potentially aggravate you and make you tense and not something upbeat. You should also have no distractions nearby and if you want to doze off you can.