LearnCube makes it easy to control an online class with the Raise Hand button on the top nav bar.

Raise Hand:

Students can press this button at any time during the class if they need to ask a question or if you’re asking them a question that you require immediate answers. This means only one student talks at a time.

As a teacher, you'll see a notification and the students avatar will bounce at the bottom of the class page. Clicking on the avatar will stop it from bouncing and "lower" the raised hand.