The section presents a question related to chemistry, specifically about elements and their states at room temperature. The key topic is the identification of the only metal that exists in a liquid state at normal temperature. The entities involved are:

- Question about a chemical element
- Options provided: 
  A. Thủy ngân (Mercury)
  B. Bac (Bismuth)
  C. Đồng (Copper)
  D. Vàng (Gold)

The correct answer is Thủy ngân (Mercury).