Answer:
The correct answer is was.
Explanation:
In the sentence, the first clause is written in past; this can be spotted by reading the verb be in singular form in past tense (was). Following this pattern, the second part refers to a singular subject (the house) and it would be incorrect to fill in the blank with were or any other tense, such as future or present (the sentence might be nonsense), turning was into the correct answer.
