“Not once has our neighbour invited us into his house.”
Our neighbour has invited us into his house not once but many times.
Our neighbour has never invited us into his house.
Correct
Occasionally our neighbour has invited us into his house
Our neighbour has not always invited us into his house.
Explanation:
Correct Answer is: Our neighbour has never invited us into his house.
Negative adverb (যেমন not once) দ্বারা বাক্য শুরু হলে inversion হয় অর্থাৎ verb + subject হয়। Not once থাকায় বাক্যটির অর্থ negative হবে।