To answer the following questions, refer to the IR spectra obtained for the four unknowns (A, B, C, and D) in lab. In the appropriate spaces below, provide: i) the vibrational stretching frequency/frequencies for the C=O bond in each unknown, ii) the name of each unknown (either benzaldehyde, benzoic acid, methyl benzoate, or benzamide), and iii) an explanation for why you identified each unknown as you did.The four unknowns are in the pictures as well below labeled A-D