Question

Which substances have both a carboxylic acid functional group and an alcohol functional group?

Answer 1

There are a lot of those. They can be recognised by name (having both "hydroxy" and "-oic acid").

Explanation:

The simplest is glycolic acid, (UPC-name: hydroxy ethanoic acid).

One you may know from everyday life is lactic acid, or officially:
2-hydroxy propanoic acid.

Citric acid is another one (but that has three acid groups).
(pictures from Wikipedia)