Which technique is used to study structure of molecules -

In the question, they have not mentioned about the nature of structure such as 1o, 2o or 3o etc. In this case, consider teiary structure (3D structure). So, mark X-ray crystallography (X-ray crystallography can detect 3-D structure of any macromolecule). ADDITIONAL INFORMATION ON THIS TOPIC Mass spectrometry: Best technique to determine-primary structure of proteins This technique is Qualitative as well as Quantitative Can detect post-translational modifications (like hydroxylation) or covalent modifications of enzymes (like phosphorylation and dephosphorylation) Can detect the exact molecular weight of the protein (as the name says - MASS).