The correct option is B Us
The correct answer is Option B.
We can make out from the word OUR that the speaker is talking of more than one person. The correct word that completes the sentence would be the relevant plural third person pronoun i.e. US. Hence Option B is the correct answer.
The remaining options are incorrect because:
Option A: OUR is a possessive pronoun and there is no meaning of possession here.
Option C and D: HER and HIS are third person singular nouns, whereas there is a reference to more than people in the given sentence (as explained above).
Hence Option B is the correct answer.