In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.

Question: Which of the following covalent bonds does not appear in proteins ?:
Options: <1> Phosphodiester linkage. <2> Amide link. <3> O-glucosidic bond. <4> Disulfide bond. <5> Hydrogen bond.
1

Question: The reaction conditions for transforming nonanamide into octanamine and carbon dioxide are:
Options: <1> H2, metallic catalyst. <2> Excess of CH3I, K2 CO3. <3> Cl2, NaOH, H2O. <4> LiAlH4, diethyl ether and then hydrolysis. <5> CH2N2, diethyl ether.
3

Question: Under the name of xanthines are grouped:
Options: <1> The coca leaf, cocaine and crack. <2> Methadone and heroin <3> The MDA and the MDMA. <4> Nicotine and inhalants. <5> Caffeine and theophylline.
5