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.