Q. Why can't my student hear audio when I play a video in Zoom

If in zoom, your students can't hear audio when you play video (such as YouTube), please make sure you select ""Share Sound" and "Optimize for video" option when you share your screen. 

please visit this google doc for a screenshot
https://docs.google.com/document/d/18yZ3xIKNeJ4cpefNa_DBmPmJo8hS2Wo-_poQjihwuJA/edit?usp=sharing

If you are using a Mac computer, you need to also make sure you uncheck "mono" under the sound source tab.