Why do only certain bases bond together in DNA?

Base pairs occur when nitrogenous bases make hydrogen bonds with each other. Each base has a specific partner: guanine with cytosine, adenine with thymine (in DNA) or adenine with uracil (in RNA). The hydrogen bonds are weak, allowing DNA to 'unzip'. This lets enzymes replicate the DNA.

Explanation:

I'm not sure thought but I think it's right just do a little more research