Combining the work of other scientists with their own research, Watson and Crick discovered that two strands of DNA join together to form a (n)

A. nucleotideB. Xinacircle. C. double helix. D. covalent bond

C. double helix

Explanation:

Watson and Crick discovered that DNA molecules are double-helical structures. According to them, each DNA molecule has two DNA strands that are wound around an imaginary axis to form a double helix. These two DNA strands are held together by complementary base pairing between their bases. They discovered that a purine base pairs with a pyrimidine base to maintain a constant distance between the two strands of a double helix.