Match the items in Group I with Group II.

Group I	Group II
P. Circular dichroism	1. Concentration
Q. X-ray crystallography	2. Sedimentation coefficient
R. Freeze-drying	3. Secondary structure determination
S. Ultracentrifugation	4. Tertiary structure determination

A. P-4, Q-1, R-2, S-3

B. P-1, Q-4, R-3, S-2

C. P-2, Q-3, R-4, S-1

D. P-3, Q-4, R-1, S-2

Answer: Option D