Which of the Following Statements Is True Regarding the Resolution $\alpha$

Multiple Choice

Which of the following statements is true regarding the resolution of x-ray structures of proteins?
I. A resolution of 5 Å is needed to observe $\alpha$ -helices as rods in an x-ray structure.
II. A resolution of 0.5 Å is needed to observe $\beta$ -sheets in an x-ray structure.
III. An x-ray structure of a protein at a resolution of 1.0 Å is considered to be high resolution.
IV. A resolution of 2.0 Å is needed to distinguish side chains of amino acids in an x-ray structure.
V. A resolution of 1.5 Å is needed to observe hydrogen atoms in an x-ray structure.

A) I and II
B) I, II, and III
C) II and V
D) I, III, IV, and V
E) None of the above