Hello!
To change singular nouns to plural nouns, you add an -s if the ending letter is a vowel. If the last letter is a consonant, you add -es.
To change plural nouns to singular nouns, you remove the -s or -es.
To change "las casas", a plural noun, into a singular noun, it would be "la casa".
Therefore, the singular form of "las casas" is la casa.
Your answer is going to be C
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