Discovering the Structure of DNA

Practice: The scientist/s that was/were given credit for first determining the structure of DNA is/are:

Practice: The scientist/s that used x-ray diffraction to help reveal the structure of DNA is/are:

Practice: In the polymerization of DNA, a phosphodiester bond is formed between a phosphate group of the nucleotide being added and which of the following atoms or molecules of the last nucleotide in the DNA strand?

Practice: Within a double-stranded DNA molecule, adenine (A) forms hydrogen bonds with thymine (T), and cytosine (C) forms hydrogen bonds with guanine (G). What is the significance of the structural arrangement?