What is the singular form of unos cuadernos

Here we have two words, unos is an indefinite article that is a determiner used to refer to a particular person or thing when the reader or listener doesn't know which one is being described, that is, when talking about something that is not defined. On the other hand, cuadernos is a masculine plural noun that means books. Therefore, we must find the singular form of the indefinite article and the noun and this is un cuaderno.

these are the words to choose from to people answer the question:

nieta--yerno--tia--tio--primo--nuera--abuelo--cunada