Answer:
There are two answers to this question. Gold or Aluminum.
 
        
             
        
        
        
Answer;
Complementary base pairs;
- Adenine-Thyamine and Guanine-Cytosine (A-T and G-C) 
Explanation;
-According to Chargaf's rule, the secondary structure of the DNA requires that every guanine pairs with a cytosine and every thymine pairs with an adenine, resulting in consistent ratios between the nucleotides. 
-In double-stranded DNA, two long molecules twist around one another in a double helix.  Pairs of nitrogenous bases are set in the same plane, and interact with each other via hydrogen bonding. These pairs are often referred to as base pairs