What does the author mean by “features” of the spike protein? “in the proximal origin of SARS-CoV-2-discussion.

https://www.nature.com/articles/s41591-020-0820-9 Read the article and then create 5 questions, the questions will be graded on creativity, originality, and thoughtfulness. Here are examples of a bad question, an okay question, and a great question.  Great question:  “How does manipulating the transmission rate affect the evolution of virulence in a horizontally transmitted pathogen?”  Bad:  ” Why is this the shortest paper I have ever read?”  okay question:  “I’m not sure what is going on with Figure 1. What does the author mean by “features” of the spike protein? “