In a complex organic chemistry research project, a team is working on elucidating the structure of an unknown organic compound, 'Compound U', which has shown promising biological activity. The structural elucidation involves a combination of advanced spectroscopic techniques. The sequence of the investigation is as follows: High-resolution mass spectrometry (HRMS) is first used to determine the molecular formula of 'Compound U'. Nuclear magnetic resonance (NMR) spectroscopy, including H NMR and C NMR, is then employed to identify the types of hydrogen and carbon environments in the molecule. Two-dimensional NMR techniques, such as COSY and HMBC, are utilized to determine the connectivity between different atoms in the molecule. Finally, infrared (IR) spectroscopy is conducted to identify specific functional groups present in 'Compound U'. Based on this sequence, what is the primary challenge or objective in the structural elucidation of 'Compound U' using these spectroscopic techniques? Options: A. Determining the molecular weight and elemental composition B. Identifying the presence of specific heteroatoms C. Establishing the complete three-dimensional structure D. Unraveling the connectivity and arrangement of atoms and functional groups Hints: Consider the type of information provided by each spectroscopic method in the context of organic compound analysis. Reflect on how mass spectrometry, NMR, and IR contribute to understanding the structure of an organic molecule. Think about the overall goal of structural elucidation in organic chemistry, especially for compounds with biological activity. Don't use chatgpt please provide valuable answer