Answer: Option (b) is the correct answer.
Step-by-step explanation:
According to naming conventions, when we write the name of a functional group then suffix is added to the new name according to the functional group present in the given compound.
For example, methanal has the suffix "al" which correspond to an aldehyde. This means that metahnal contains an aldehyde group.
Thus, we can conclude that according to naming conventions, aldehydes is the class of organic compounds to which methanal belong to.