She lives in________nice small house

The correct answer is "a." The sentence should read, "She lives in a nice small house."

In English, the article "a" is used before singular nouns that begin with a consonant sound. The phrase "nice small house" is referring to one house, and since it starts with a consonant sound ("h" in "house"), "a" is the appropriate article to use.

Using "an" would be incorrect here because "an" is used before words that start with a vowel sound. Since "nice small house" is singular and not specified as a particular house, "a" is correct. Therefore, the final sentence clearly indicates that she lives in one small house that is described as nice.