(a) The general name for the organic compounds comprising -CO- is ketones.
(b) CH3COOH is the compound which contains a carboxylic acid group (-COOH).
(c) The name of the compound is methanal, as the structure contains one carbon atom and an aldehyde group (-CHO), which is indicated by using 'al' as the suffix. Hence, replacing the last letter 'e' of methane with 'al' we get the name methanal.