**1. Introduction**

The sudden outbreak of COVID-19 in China in 2019 during the Spring Festival, has spread rapidly worldwide [1]. The disease spread relatively fast and affected the whole world [2]. The COVID-19 has now become a global issue [3]. Several measures have been taken to prevent physical contact during the pandemic and contain the spread of COVID-19. The most stringent step for epidemic prevention is lockdown [4], which aims to restrict the movement/mobility of people. Colleges and universities are also facing unprecedented challenges. The pandemic has forced the closure of schools, and more and more universities have to turn to online learning [5]. Several studies indicated that online learning displays the potential of overcoming course delivery difficulties during the pandemic of COVID-19. For example, Guo [6] found that physics students have a better performance in introductory calculus class as

attending the online sessions than those absent in online sessions and only rely on self-learning materials. More students attending online sessions believe that synchronous online sessions are the same as face-to-face teaching compared to their counterparts since those sessions allow students to interact with the teacher. This implies that engagement during lectures will be an important factor to facilitate students' study.
