#a.# #"Ethyl alcohol is LESS volatile than ethylamine."#
#b.# #"Ethyl alcohol is LESS volatile than dimethyl ether."#
#c.# #"Ethyl alcohol is LESS volatile than ethane."#
For #b.# and #c.#, the capacity of ethyl alcohol to hydrogen-bond, which constitutes a quite potent force of intermolecular interaction, can rationalize the involatility of the alcohol.
#"Ethyl alcohol"# is LESS volatile than #"ethylamine"#, in that the strength of hydrogen bonding, of intermolecular interaction, is reasonably weaker in that the #N-H# is less polar, less charge-separated than the #O-H# bond.
But a physical scientist should always argue on the basis of data, which we ain't got here. I list the normal boiling points of each substance (which the question should probably have supplied, and asked you to rationalize:)
#"Ethane,"# #-89# #""^@C#;
#"Dimethyl ether,"# #-24# #""^@C#;
#"Ethylamine,"# #+16# #""^@C#;
#"Ethyl alcohol,"# #+78.4# #""^@C#.
Are these data consistent with the degree of intermolecular force as argued?