Add a concert a solo clarinet for former keeps running out of breath before finishing a part of the melody what could be a possible cause of this problem

The clarinet soloist is not taking the proper breaths before starting his or her part. The soloist needs to take a proper breath support, a low breath. make sure the shoulders do not rise when taking a low breath and your stomach is the only thing that expands. Do not push so much air out when playing but just enough, and make sure you do not breath through your nose either when playing.

Aa i believe is the answer to your question