Final answer:
The verb 'isn't' correctly completes the sentence 'The house _____ too big' since it agrees with the singular subject 'the house'.
Step-by-step explanation:
The verb that correctly completes the sentence 'The house _____ too big' is 'isn't'.
In this sentence, the subject 'the house' is singular, so the verb needs to agree with the singular subject. Therefore, the correct verb form to use is 'isn't', which is the contraction of 'is not'. The options 'aren’t', 'weren’t', 'don’t', and 'haven’t' are either plural forms or are not to be used with the subject 'the house' in the context of this sentence.
'The house isn't too big'
is the correct version of the sentence.