Soda is sweet. Anything sweet contains sugar. When Xing has too much sugar, he could go mad. And the cup is almost empty. While his fingers fiddling with the cup, Xing's legs shake vigorously. It is unclear whether this class really excites him or that he is about to go crazy. Then the professor whatever her name is shows another portrait.

O___o

Uncle Sylvester?

With an obvious accent, "Professor! That look a lot like my Uncle Sylvester. Do you know him?" he speaks out after putting up his hand. His facial expression is that of a naive kid who doesn't even know what is he talking about.