Answer the following question given this paragraph: 

The binding of complementary bases allows DNA molecules to take their well-known shape, called a double helix . Figure below shows how two chains of nucleotides form a DNA double helix. A simplified double helix is illustrated in Figure below . It shows more clearly how the two chains are intertwined. The double helix shape forms naturally and is very strong. Being intertwined, the two chains are difficult to break apart. This is important given the fundamental role of DNA in all living organisms.


Q: The binding of complementary bases allows dna molecules to take their well-known shape, called a what?

 Choices:

- triple helix

- single helix

- simple helix

- double helix

A:
double helix
