The section presents a multiple-choice question regarding the chemical element with the symbol "Hg." The options provided are:

A. Thủy ngân (Mercury)  
B. Bạc (Silver)  
C. Vàng (Gold)  
D. Đồng (Copper)  

The correct answer is A. Thủy ngân. The key topics include chemical elements and their symbols, specifically focusing on the element mercury.