Explanation: subjunctive is a mood of verbs that expresses what is imagined or wished or possible (something hypothetical). From the given options, the change that corrects the sentence, is the corresponding to option A: change was to were, because the sentence is expressing a hypothetical situation (a wish) so it should be in subjunctive mood, and the subjunctive of the verb to be is "were" the correct sentence would be: if the house were less expensive, we would be able to buy it.
