The correct option is
A Our
In order to fill in the blank with the correct personal pronoun, let us understand what personal pronouns are. We use personal pronouns in place of a particular thing or a person's name/noun. For example: 'I spoke to them'. Here, 'I' is a subjective personal pronoun and 'them' is an objective personal pronoun.
NOTE: The first blank requires an objective personal pronoun for 'we'.
Option A - 'Mine' is used as an objective personal pronoun for 'me'. Hence, option A is incorrect.
Option C - 'His' is used as an objective personal pronoun for 'he'. 'His' is used to indicate any possession or ownership of a male noun/pronoun. Hence, option C is incorrect.
Option D - 'Him' is used as an objective personal pronoun for 'he'. Hence, option D is incorrect.
Option B - 'Our' is used as an objective personal pronoun for the subjective personal pronoun 'we'. It is used to express ownership. Hence, option B is the correct answer.
'Yesterday we entered our new house.'