The correct answer is: A. a
The word "a" is used before singular nouns that refer to a general or indefinite thing or person. In this case, the speaker is buying a house that is not specific or unique.
The word "an" is used before singular nouns that begin with a vowel sound. In this case, the house does not begin with a vowel sound, so "an" would not be the correct answer.
The word "the" is used before singular nouns that refer to a specific or unique thing or person. In this case, the speaker is not buying a specific or unique house, so "the" would not be the correct answer.
The word "none of these" is not the correct answer because the speaker is buying a house.
