The section presents a question regarding the atomic number of a chemical element. It asks which element has an atomic number of 26, providing four options: 

A. Iron (Sắt)  
B. Nickel (Nickel)  
C. Chromium (Crom)  
D. Manganese (Mangan)  

Key topics include atomic numbers and chemical elements, while the key entities are the elements listed in the options.